Wikipedia:Manual of Style/Dates and numbers

This part of the Manual of Style aims to achieve consistency in the use and formatting of dates and numbers in Wikipedia articles. Consistent standards make articles easier to read, write and edit. Where this manual provides options, consistency should be maintained within an article, unless there is a good reason to do otherwise. In direct quotations, the original text should be preserved.

In June 2005, the Arbitration Committee stated that when either of two styles is acceptable, it is inappropriate for an editor to change an article from one to the other without substantial reason. For example, with respect to British date formats as opposed to American it would be acceptable to change from American format to British if the article concerned a British subject. Edit warring over optional styles (such as 14 February and February 14) is unacceptable. If an article has been stable in a given style, it should not be converted without a style-independent reason. Where in doubt, defer to the style used by the first major contributor.

Non-breaking spaces

See also: Wikipedia:Line break handling and Wikipedia:Manual of Style#Non-breaking spaces

• Wikipedia recommends the use of a non-breaking space (also known as a hard space) when necessary to prevent the end-of-line displacement of elements that would be awkward at the beginning of a new line:
  • in compound expressions in which figures and abbreviations or symbols are separated by a space (17 kg, AD 565, 2:50 pm);
  • on the left side of spaced en dashes, if necessary for comprehension; and
  • in other places where displacement might be disruptive to the reader, such as £11 billion, 5° 24′ 21.12″ N, Boeing 747, and the first two items in 7 World Trade Center.
  • Roman numerals at the end of phrases such as World War II or Pope Benedict XVI
• A hard space can be produced with the HTML code   instead of the space bar: 19 kg yields a non-breaking 19 kg.
• A literal hard space should not be used since some browsers will not load them properly when editing.
• Hard spaces can also be produced by using the {{nowrap}} template: {{nowrap|8 sq ft}} produces a non-breaking 8 sq ft. This is especially useful for short constructions requiring two or more hard spaces, as in the preceding example. Template {{nowrap}} has the disadvantage that if the enclosed text starts or ends with a space, these spaces are forced outside in the resulting HTML, and unpredicted breaks may occur. If   occurs right before {{nowrap}}, or at the start of text within {{nowrap}}, some browsers allow a break at that point.
• In some older browsers, quotation marks separated by a hard space are broken at the end of a line: (She said 'Yes!' ).
• Unlike normal spaces, multiple hard spaces are not compressed by browsers into a single space.

Chronological items

Precise language

See also: Wikipedia:As of

Avoid statements that will date quickly, except on pages that are regularly updated, such as those that cover current events. Avoid such items as now and soon (unless their intended meaning is clear), currently and recently (except on rare occasions where they are not redundant), or phrases such as in modern times and the sixties. Instead, when writing about past events use more precise phrases such as during the 1990s, or in August 1969. For future and current events use phrases such as as of March 2024, or since the start of 2005 which indicate the time-dependence of the information to the reader.

To assist editors in keeping the information up to date, statements about future and current events may be used in conjunction with the "as of" technique. This is done using the {{as of}} template to tag information that may become dated quickly: {{as of|2024}} produces the text As of 2024 and categorises the article appropriately. However, this technique is not an alternative to using precise language. For instance, one should not replace "since the start of 2005" with {{as of|2005}} because some information (the start of 2005) would be lost.

Time of day

Context determines whether the 12- or 24-hour clock is used; in both, colons separate hours, minutes and seconds (1:38:09 pm and 13:38:09).

• 12-hour clock times end with dotted or undotted lower-case a.m. or p.m., or am or pm, which are spaced (2:30 p.m. or 2:30 pm, not 2:30p.m. or 2:30pm). Noon and midnight are used rather than 12 pm and 12 am; whether midnight refers to the start or the end of a date will need to be specified unless this is clear from the context.
• 24-hour clock times have no a.m., p.m., noon or midnight suffix. Discretion may be used as to whether the hour has a leading zero (08:15 or 8:15). 00:00 refers to midnight at the start of a date, 12:00 to noon, and 24:00 to midnight at the end of a date but should not be used for the first hour of the next day e.g. use 00:10 for ten minutes after midnight, not 24:10.

Time of day is normally expressed in figures rather than being spelled out. For further information and information on time intervals (e.g. 5 minutes) see the "Numbers as figures or words" section.

Day, month and season names

See Wikipedia:Manual of Style (capital letters)#Calendar items

This part of the Manual of Style aims to achieve consistency in the use and formatting of dates and numbers in Wikipedia articles. Consistent standards make articles easier to read, write and edit. Where this manual provides options, consistency should be maintained within an article, unless there is a good reason to do otherwise. In direct quotations, the original text should be preserved.

In June 2005, the Arbitration Committee stated that when either of two styles is acceptable, it is inappropriate for an editor to change an article from one to the other without substantial reason. For example, with respect to British date formats as opposed to American it would be acceptable to change from American format to British if the article concerned a British subject. Edit warring over optional styles (such as 14 February and February 14) is unacceptable. If an article has been stable in a given style, it should not be converted without a style-independent reason. Where in doubt, defer to the style used by the first major contributor.

Non-breaking spaces

See also: Wikipedia:Line break handling and Wikipedia:Manual of Style#Non-breaking spaces

• Wikipedia recommends the use of a non-breaking space (also known as a hard space) when necessary to prevent the end-of-line displacement of elements that would be awkward at the beginning of a new line:
  • in compound expressions in which figures and abbreviations or symbols are separated by a space (17 kg, AD 565, 2:50 pm);
  • on the left side of spaced en dashes, if necessary for comprehension; and
  • in other places where displacement might be disruptive to the reader, such as £11 billion, 5° 24′ 21.12″ N, Boeing 747, and the first two items in 7 World Trade Center.
  • Roman numerals at the end of phrases such as World War II or Pope Benedict XVI
• A hard space can be produced with the HTML code   instead of the space bar: 19 kg yields a non-breaking 19 kg.
• A literal hard space should not be used since some browsers will not load them properly when editing.
• Hard spaces can also be produced by using the {{nowrap}} template: {{nowrap|8 sq ft}} produces a non-breaking 8 sq ft. This is especially useful for short constructions requiring two or more hard spaces, as in the preceding example. Template {{nowrap}} has the disadvantage that if the enclosed text starts or ends with a space, these spaces are forced outside in the resulting HTML, and unpredicted breaks may occur. If   occurs right before {{nowrap}}, or at the start of text within {{nowrap}}, some browsers allow a break at that point.
• In some older browsers, quotation marks separated by a hard space are broken at the end of a line: (She said 'Yes!' ).
• Unlike normal spaces, multiple hard spaces are not compressed by browsers into a single space.

Chronological items

Precise language

See also: Wikipedia:As of

Avoid statements that will date quickly, except on pages that are regularly updated, such as those that cover current events. Avoid such items as now and soon (unless their intended meaning is clear), currently and recently (except on rare occasions where they are not redundant), or phrases such as in modern times and the sixties. Instead, when writing about past events use more precise phrases such as during the 1990s, or in August 1969. For future and current events use phrases such as as of March 2024, or since the start of 2005 which indicate the time-dependence of the information to the reader.

To assist editors in keeping the information up to date, statements about future and current events may be used in conjunction with the "as of" technique. This is done using the {{as of}} template to tag information that may become dated quickly: {{as of|2024}} produces the text As of 2024 and categorises the article appropriately. However, this technique is not an alternative to using precise language. For instance, one should not replace "since the start of 2005" with {{as of|2005}} because some information (the start of 2005) would be lost.

Time of day

Context determines whether the 12- or 24-hour clock is used; in both, colons separate hours, minutes and seconds (1:38:09 pm and 13:38:09).

• 12-hour clock times end with dotted or undotted lower-case a.m. or p.m., or am or pm, which are spaced (2:30 p.m. or 2:30 pm, not 2:30p.m. or 2:30pm). Noon and midnight are used rather than 12 pm and 12 am; whether midnight refers to the start or the end of a date will need to be specified unless this is clear from the context.
• 24-hour clock times have no a.m., p.m., noon or midnight suffix. Discretion may be used as to whether the hour has a leading zero (08:15 or 8:15). 00:00 refers to midnight at the start of a date, 12:00 to noon, and 24:00 to midnight at the end of a date but should not be used for the first hour of the next day e.g. use 00:10 for ten minutes after midnight, not 24:10.

Time of day is normally expressed in figures rather than being spelled out. For further information and information on time intervals (e.g. 5 minutes) see the "Numbers as figures or words" section.

Day, month and season names

See Wikipedia:Manual of Style (capital letters)#Calendar items

Longer periods

• Months are expressed as whole words (February, not 2), except in the ISO 8601 format; unlike in some other languages, names of months (and of days of the week) are capitalized in English. Abbreviations such as Feb are used only where space is extremely limited, such as in tables and infoboxes. Do not insert of between a month and a year (April 2000, not April of 2000).
• Seasons. Because the seasons are not simply reversed in each hemisphere – and areas near the equator tend to have just wet and dry seasons – neutral wording may be preferable (in early 1990, in the second quarter of 2003, around September). Use a date or month rather than a season name, unless there is a logical connection (the autumn harvest). Seasons are normally spelled with a lower-case initial.
• Years
  • Years are normally expressed in digits. Avoid inserting the words the year before the digits (1995, not the year 1995), unless the meaning would otherwise be unclear.
  • Year ranges, like all ranges, are separated by an en dash, not a hyphen or slash: 2005–06 is a two-year range, whereas 2005/06 is a period of twelve months or less such as a sports season or a financial year. A closing CE/AD year is normally written with two digits (1881–86) unless it is in a different century from that of the opening year (1881–1986). The full closing year is acceptable, but abbreviating it to a single digit (1881–6) or three digits (1881–886) is not. A closing BCE or BC year is given in full (2590–2550 BCE). While one era signifier at the end of a date range requires an unspaced en dash (12–5 BC), a spaced en dash is required when a signifier is used after the opening and closing years (5 BC – AD 29).
  • To indicate around/approximately/about, the abbreviations c. and ca. are preferred over circa, approximately or approx., and are spaced (c. 1291). Do not use a question mark for this function (1291?), as this may imply to the reader an uncertainty on the part of Wikipedia editors rather than on the part of reliable historians.
• Decades
  • Decades as such contain no apostrophe (the 1980s, not the 1980's). The two-digit form is never used in reference to the decade as a time span per se.
  • The two-digit style, to which a preceding apostrophe is typically added, is used only in reference to a social era or cultural phenomenon that roughly corresponds to and is said to define a decade, and only if it is used in a sourceable stock phrase (the Roaring '20s, the Gay '90s), or when there is a notable connection between the period and what is being discussed in the sentence (a sense of social justice informed by '60s counterculture, but grew up in 1960s Boston, moving to Dallas in 1971). Such an abbreviation should not be used if it would be redundant ('80s Reaganomics) or if it does not have a clear cultural significance and usage (the '10s).
• Centuries and millennia
  • For purposes of written style, the English Wikipedia does not recognize a year 0. Therefore, for dates AD (or CE) the 1st century was 1–100, the 17th century was 1601–1700, and the second millennium was 1001–2000; for dates BC (or BCE) the 1st century was 100–1; the 17th century was 1700–1601, and the second millennium was 2000–1001.
  • Forms such as the 1700s are normally best avoided (although the difference in meaning should be noted: the 1700s is 1700–1799, whereas the 18th century is 1701–1800).

Year numbering systems

• Years are numbered according to the traditional western Dionysian era ("Common Era").
  • AD and BC are the traditional ways of referring to these eras. However, the CE and BCE is becoming more common in academic and some religious writing. No preference is given to either style.
    • Do not use CE or AD unless the date would be ambiguous without it. e.g. "The Norman Conquest took place in 1066." not 1066 CE or AD 1066.
    • BCE and CE or BC and AD are written, in upper case, spaced, and without periods (full stops).
    • Use either the BC-AD or the BCE-CE notation, but not both in the same article. AD may appear before or after a year (AD 106, 106 AD); the other abbreviations appear after (106 CE, 3700 BCE, 3700 BC).
    • Do not change from one style to another unless there is substantial reason for the change, and consensus for the change with other editors.
• Uncalibrated (bce) radiocarbon dates: Some source materials will indicate whether a date is calibrated or not simply by a change in capitalization; this is often a source of confusion for the unwary reader. Do not give uncalibrated radiocarbon dates (represented by the lower-case bce unit, occasionally bc or b.c. in some sources), except in directly quoted material, and even then include a footnote, a square-bracketed editor's note [like this], or other indication to the reader what the calibrated date is, or at least that the date is uncalibrated. Calibrated and uncalibrated dates can diverge surprisingly widely, and the average reader does not recognize the distinction between bce and BCE / BC.
• Abbreviations indicating long periods of time ago—such as BP (before present), as well as various annum-based units such as ka (kiloannum), Ma (megaannum) and Ga (gigaannum) are given as full words on first occurrence. Where source quotations use the abbreviations kya (thousand years ago), mya (million years ago), or bya (billion years ago) this should be explained to the reader, as in "a measured Libby radiocarbon date of 35.1 mya [million years ago] had to be calibrated ..." The kya, mya and bya symbols are deprecated in some fields such as geophysics and geology, but remain common in others, such as anthropology.
  • BP: Do not convert other notations to BP unless you are certain of what you are doing. In some contexts the unit BP is actually defined as "years before January 1, 1950", not "years before the literal present", and the conversion may introduce an error if the date being converted is not a wide approximation (18,000 BP) but a more narrow one or an actual known year. BP years are given as 18,000 BP or spelled out as 18,000 years before present (not 18,000 YBP, 18,000 before present, 18,000 years before the present, or similar.)

Calendars

See also: Old Style and New Style dates

Dates can be given in any appropriate calendar, as long as the date in either the Julian or Gregorian calendars is provided, as described below. For example, an article on the early history of Islam may give dates in both Islamic and Julian calendars. Where a calendar other than the Julian or Gregorian is used, this must be clear to readers.

• Current events are given in the Gregorian calendar.
• Dates before the adoption of the Gregorian calendar on 15 October 1582 are normally given in the Julian calendar. The Julian day and month should not be converted to the Gregorian calendar, but the start of the Julian year should be assumed to be 1 January (see below for more details).
• Dates for Roman history before 45 BC are given in the Roman calendar, which was neither Julian nor Gregorian. When (rarely) the Julian equivalent is certain, it may be included.
• The Julian or Gregorian equivalent of dates in early Egyptian and Mesopotamian history is often debatable. Follow the consensus of reliable sources, or indicate their divergence.
• Dates of events in countries using the Gregorian calendar are given in the Gregorian calendar. This includes some of the Continent of Europe from 1582, the British Empire from 14 September 1752, and Russia from 14 February 1918 (see the Gregorian calendar article).

The dating method used in a Wikipedia article should follow that used by reliable secondary sources. If the reliable secondary sources disagree, choose the most common used by reliable secondary sources and note the usage in a footnote.

At some places and times, dates other than 1 January were used as the start of the year. The most common English-language convention was the Annunciation Style used in Britain and its colonies, in which the year started on 25 March, Annunciation Day; see the New Year article for a list of other styles. 1 January is assumed to be the opening date for years; if there is reason to use another start-date, this should be stated.

If there is a need to mention Old Style or New Style dates in an article (as in the Glorious Revolution), a footnote should be provided on the first usage, stating whether the "New Style" refers to a start of year adjustment or to the Gregorian calendar (it can mean either).

Time zones

When writing a date, first consider where the event happened and use the time zone there. For example, the date of the Attack on Pearl Harbor should be December 7, 1941 (Hawaii time/date). If it is difficult to judge where, consider what is significant. For example, if a vandal based in Japan attacked a Pentagon computer in the US, use the time zone for the Pentagon, where the attack had its effect. If known, include the UTC date and time of the event in the article, indicating that it is UTC.

Numbers

Numbers as figures or words

As a general rule, in the body of an article, single-digit whole numbers from zero to nine are spelled out in words; numbers greater than nine are commonly rendered in numerals, or may be rendered in words if they are expressed in one or two words (16 or sixteen, 84 or eighty-four, 200 or two hundred, but 3.75, 544, 21 million). This applies to ordinal numbers as well as cardinal numbers. However there are frequent exceptions to these rules.

• In tables and infoboxes, quantitative data is expressed as numerals; numerals will also fit better in limited space. Numbers within a table's explanatory text and comments should be consistent with the general rule.
• Comparable quantities should be all spelled out or all figures: we may write either 5 cats and 32 dogs or five cats and thirty-two dogs, not five cats and 32 dogs.
• Adjacent quantities which are not comparable should usually be in different formats: twelve 90-minute volumes or 12 ninety-minute volumes is more readable than 12 90-minute volumes or twelve ninety-minute volumes.
• Numbers that begin a sentence are spelled out, since using figures risks the period being read as a decimal point or abbreviation mark; it is often better to recast the sentence than to simply change format, which may produce other problems: e.g., do not use Nineteen forty five and 1950 were important elections for the Labour Party, but rather The elections of 1945 and 1950 were important for the Labour Party.
• The numerical elements of dates and times are not normally spelled out (that is, do not use the seventh of January or twelve forty-five p.m. or Two thousand eight was the year that ... ). However, they should be spelled out where customary in historical references such as Seventh of March Speech and Fifth of November; these are treated as proper names.
• Centuries are named in figures: (the 5th century CE; 19th-century painting); when the adjective is hyphenated, consider nineteenth-century painting, but not when contrasted with painting in the 20th century.
• Simple fractions are normally spelled out; use the fraction form if they occur in a percentage or with an abbreviated unit (1⁄8 mm or an eighth of a millimeter, but not an eighth of a mm) or if they are mixed with whole numerals.
• Decimal representations containing a decimal point are not spelled out (1.00, 3.14159).
• Numbers in mathematical formulae are never spelled out ("3 < π < 22/7", not "three < π < 22 sevenths").
• Do not use spelled-out numbers before symbols for units of measurement: write five minutes, 5 minutes, or 5 min, but not five min.
• Measurements, stock prices, and other quasi-continuous quantities are normally stated in figures, even when the value is a small positive integer: 9 mm, The option price fell to 5 within three hours after the announcement.
• When expressing large approximate quantities, it is preferable to write them spelled out, or partly in figures and part as a spelled‑out named number; e.g., one hundred thousand troops may be preferable to 100,000 troops when the size of the force is not known exactly; write Japan has the world's tenth largest population, with about 128 million people (as it is just an approximation to a number likely to be anywhere between 127,500,000 and 128,500,000), but The movie grossed $28,106,731 on its opening day (the exact quantity).
• When both a figure and spelled-out named number are used in a quantity, it is useful to use a non-breaking space, as in 128 million or 128{{nbsp}}million to prevent a line break from occurring between them.
• Sometimes figures and words may carry different meanings, for example Every number except one implies that there is one exception (we don't know which), while Every number except 1 means that the specific number 1 is the exception.
• Proper names, formal numerical designations, and other idioms comply with common usage: e.g., write Chanel No. 5, 4 Main Street, 1-Naphthylamine, Channel 6, Fourth Amendment, Seventeenth Judicial District, Seven Years' War. This is the case even where it causes a numeral to open a sentence, although this is usually avoided by rewording.

Typography

• Spelled-out two-word numbers from 21 to 99 are hyphenated (fifty-six), as are fractions (seven-eighths). Do not hyphenate other multi-word numbers (five hundred, not five-hundred).
• Where a whole number in a percentage is spelled out, the percent sign is not used (three percent or 3%, not three %).
• The ordinal suffix (e.g., th) is not superscripted (23rd and 496th, not 23^rd and 496^th).

Large numbers

See also: Order of magnitude and Long and short scales

• In a number with many digits, digit grouping symbols (inserted at intervals from the decimal point) should be used to subdivide the number into easily readable groups. The acceptable digit grouping schemes are:
  • Commas every three digits to the left of the decimal point, and no grouping to the right of the decimal point (e.g. 8,274,527 or 0.12345). This is traditional usage in many English-language contexts.
  • Thin, non-breaking spaces every three digits (e.g. 8274527 or 0.12345). This format is suggested in BIPM and NIST style guides for scientific and engineering works, and is in common use in interlanguage contexts. The {{gaps}} template uses CSS to produce this output (using the syntax {{gaps|8|274|527}}). Using HTML entities for this purpose (e.g.   or  ) may cause rendering problems in some browsers, and should be avoided when practical.
  • Other traditional digit grouping schemes, when relevant to the subject matter of the article (e.g. 82,74,527 in the Indian numbering system, or 3.141592653589793238462643383279… for long truncated representations of mathematical constants).
  • When a number has exactly four digits on any side of the decimal separator, those digits may optionally be expressed as a group of four instead of three (e.g. both 9876 and 9,876 are acceptable, although commas or spaces are not used in four-digit years, page numbers, and addresses).
• Large round numbers are generally assumed to be approximations; only where the approximation could be misleading is it necessary to qualify with words such as "about".
• Avoid overly precise values where they are unlikely to be stable or accurate, or where the precision is unnecessary in the context. The sentence The speed of light in a vacuum is 299,792,458 metres per second may well be appropriate since it is defined as precisely that value; The distance from the Earth to the Sun is 149,014,769 kilometres and The population of Cape Town is 2,968,790 people would usually not be, because both values are unstable at that level of precision, and readers are unlikely to care in the context.
• Scientific notation, e.g. 5.8×10⁷ kg, is preferred in scientific contexts; editors can use the {{val}} template, which generates such expressions with the syntax {{val|5.8|e=7|u=kg}}.
• Where values in the millions occur a number of times through an article, upper-case "M" may be used for "million", unspaced, after spelling out the first occurrence, e.g. She bequeathed her fortune of £100 million unequally: her eldest daughter received £70M, her husband £18M, and her three sons £4M each.
• The named numbers, billion and trillion are understood to be “short scale”, 10⁹ and 10¹², respectively (see Long and short scales). After the first occurrence in an article, "billion" may be abbreviated to unspaced "bn" ($35bn).

Fractions

The template {{frac}} is available for representing common fractions. For p⁄q, type {{frac|p|q}}. For N+p⁄q, type {{frac|N|p|q}}. When copied and pasted, the latter text will appear as N+p/q.

Decimal points

• A decimal point is used between the integer and the fractional parts of a decimal; a comma is never used in this role (6.57, not 6,57).
• The number of decimal places should be consistent within a list or context (The response rates were 41.0 and 47.4 percent, respectively, not The response rates were 41 and 47.4 percent, respectively).
• Numbers between −1 and +1 require a leading zero (0.02, not .02); exceptions are sporting performance averages (.430 batting average) and commonly used terms such as .22 caliber.

Percentages

• Percent or per cent are commonly used to indicate percentages in the body of an article. The symbol % is more common in scientific or technical articles and in complex listings.
• The symbol is unspaced (71%, not 71 %).
• In tables and infoboxes, the symbol % is normally preferred to the spelled-out percent or per cent.
• Ranges are preferably formatted with one rather than two percentage signifiers (22–28%, not 22%–28%).
• Avoid ambiguity in expressing a change of rates. This can be done by using percentage points, not percentages, to express a change in a percentage or the difference between two percentages; for example, "The agent raised the commission by five percentage points, from 10 to 15%" (if the 10% commission had instead been raised by 5%, the new rate would have been 10.5%). It is often possible to recast the sentence to avoid the ambiguity ("made the commission larger by half."). Percentage point should not be confused with basis point, which is a hundredth of a percentage point.

Natural numbers

The set of natural numbers has two common meanings: {0, 1, 2, 3, ...}, which may also be called non-negative integers, and {1, 2, 3, ...}, which may also be called positive integers. Use the sense appropriate to the field to which the subject of the article belongs if the field has a preferred convention. If the sense is unclear, and if it is important whether or not zero is included, consider using one of the alternative phrases rather than natural numbers if the context permits.

Repeating decimals

The preferred way to indicate a repeating decimal is to place a bar over the digits that repeat. To achieve this the template {{overline}} can be used. For example, the markup 14.{{overline|285714}} gives "14.285714".

Consider a short explanation of the notation the first time this notation is used in an article. Some authors place the repeating digits in parentheses rather than using an overbar (perhaps because overbars are not available in their typesetting environment) but this should be avoided in Wikipedia to avoid confusion with expressing uncertainty.

Non-base-10 notations

For numbers expressed in bases other than base ten:

• In computer-related articles, use the C programming language prefixes 0x (zero-ex) for hexadecimal and 0 (zero) for octal. For binary, use 0b. Consider including a note at the top of the page about these prefixes.
• In all other articles, use subscript notation. For example: 137₉, 241₆, 2A9₁₂, A87D₁₆ (use <sub> and </sub>).
• For base eleven and higher, use whatever symbols are conventional for that base. One quite common convention, especially for base 16, is to use upper-case A–F for digits from 10 through 15 (0x5AB3).

Scientific notation, engineering notation, and uncertainty

Notations

• The template {{val}} can be used to facilitate the generation of scientific notation. It is a flexible tool that allows editors great latitude and must have arguments (each section between the vertical bars) properly entered in order for it to generate output that is compliant with formating conventions.
• Scientific notation is done in the format of one leading digit/decimal marker/rest of digits/×10ⁿ, where n is the integer that gives one leading digit.
  • 1.602×10⁻¹⁹ is a proper use of scientific notation.
  • 160.2×10⁻¹⁷ is not a proper use of scientific notation.
• Engineering notation is done in the format of leading digits/decimal marker/rest of digits/×10ⁿ, where n is a multiple of 3. The number of leading digits is adjusted accordingly.
  • 132.23×10⁶ is a proper use of engineering notation.
  • 1.3223×10⁸ is a not proper use of engineering notation.
• It is clearer to avoid mixing scientific notation and engineering notation in the same context (e.g., do not write A 2.23×10² m² region covered by 234.0×10⁶ grains of sand).
• Use discretion when it comes to using scientific and engineering notation. Not all values need to be written in it.
  • Sometimes it is useful to compare values with the same power of 10 (often in tables) and scientific or engineering notation might not be appropriate.

Uncertainty

• Uncertainties can be written in various ways:
  • Value/±/uncertainty/×/10ⁿ/unit symbol (e.g., (1.534±0.35)×10²³ m)
    • Do not group value and uncertainty in parenthesis before the multiplier (e.g., do not write (15.34 ± 0.35) × 10²³ m)
  • Value/superscript positive uncertainty/subscript negative uncertainty/×/10ⁿ/unit symbol (e.g., 15.34+0.43
    −0.23×10²³ m)
  • Value(uncertainty in the last digits)/×/10ⁿ/unit symbol (e.g., 1.604(48)×10⁻⁴ J)
  • Value/±/relative uncertainty(percent)/unit symbol (e.g., 12.34 ± 5% m²)
• The template {{val}} may be used to automatically handle all of this.

Units of measurement

The use of units of measurement is based on the following principles:

• Avoid ambiguity: Aim to write so you cannot be misunderstood.
• Familiarity: The less readers have to look up definitions, the easier it is to be understood.
• International scope: Wikipedia is not country-specific; apart from region-specific topics, use internationally accepted units for the topic at hand.

If there is trouble balancing these bullets, consult other editors through the talk page and try to reach consensus.

Adopting suggestions from standards bodies: You might wonder why Wikipedia’s style guides have not always adopted the suggestions of internationally recognized standards bodies. The objective of any encyclopedia is to communicate to its readership with minimal confusion. Sometimes, real-world practices do not follow the suggestions of standards bodies such as the BIPM and their SI, the IEC, and the ISO. When that occurs, Wikipedia typically follows the real‑world practice so our articles read naturally and there is minimal confusion.

For instance, the real world—and therefore Wikipedia too—flouts SI writing style regarding the percent (%) symbol. According to the BIPM’s SI brochure: Subsection 5.3.3, Formatting the value of a quantity, a space is always used to separate the unit symbol from the numeric value. Notable exceptions are the unit symbols for degree, minute, and second for plane angle, °, ′, and ″ (e.g., a latitude of 47° 38′ 8.8″). However, according to their SI brochure: 5.3.7 Stating values of dimensionless quantities, or quantities of dimension one, the exception does not apply to the “%” symbol; it states as follows: “When it [the percent symbol] is used, a space separates the number and the symbol %.” This practice has not been well adopted with regard to the % symbol, is contrary to Wikipedia’s Manual of Style, and editors are asked to abide by this style guide so that our articles read most naturally. It is 50%, not 50 %.

Wikipedia similarly follows real-world practices with the binary prefixes (megabyte, kilobyte) and their unit symbols (MB and KB respectively). This practice ignores the fact that the IEC in 1998 proposed new binary prefixes for the world to adopt. Their proposal introduced new units of measure like mebibyte (symbol: MiB) and kibibyte (symbol: KiB). Again, consistent with our objective of communicating to our readership with minimal confusion, Wikipedia follows the real‑world practice observed by the computing world when they communicate to a general‑interest audience. It is 256 MB of RAM, not 256 MiB of RAM. In order to communicate with minimal confusion to its readership, Wikipedia follows real‑world practices and does not endeavor to promote change by attempting to lead by example.

Which units to use

• In articles which are not region-specific, prefer internationally accepted units. Usually, they are the units of the International System of Units (SI) and non-SI units accepted for use with SI; but there are various exceptions for particular classes of measurements. However:
  • in US-specific topics, the primary units are generally US customary units, with conversions given into SI and related units;
  • UK-related topics may have either SI or imperial units as the primary units.
• Generally, use units consistently (e.g., write a 10-kilogram (22 lb) bag of potatoes and a 5 kg (11 lb) bag of carrots, not a 10-kilogram (22 lb) bag of potatoes and a 11-pound (5 kg) bag of carrots).
  • Nominal and defined values should be given in the original units first, even if this makes the article inconsistent: for example, When the Republic of Ireland adopted the metric system, the road speed limit in built-up areas was changed from 30 miles per hour (48 km/h) to 50 kilometres per hour (31 mph). (The focus is on the change of units, not on the 3.6% increase.)
• If editors cannot agree on the sequence of units, put the source value first and the converted value second. If the choice of units is arbitrary, use SI units as the main unit, with converted units in parentheses.
• Use familiar units rather than obscure units—do not write over the heads of the readership (e.g., a general interest topic such as black holes would best be served by having mass expressed in solar masses, but it might be appropriate to use Planck units in an article on the mathematics of black hole evaporation).
• Some disciplines use units not approved by the BIPM, or write them differently from BIPM-prescribed format. When a clear majority of the sources relevant to those disciplines use such units, articles should follow this (e.g., using cc in automotive articles and not cm³). Such use of non-standard units are always linked on first use.
• In scientific articles, use the units employed in the current scientific literature on that topic. This will usually be SI, but not always; for example, natural units are often used in relativistic and quantum physics, and Hubble's constant should be quoted in its most common unit of (km/s)/Mpc rather than its SI unit of s⁻¹.
• Avoid ambiguous unit names (e.g., write imperial gallon or US gallon rather than gallon). Only in the rarest of instances should ambiguous units be used, such as in direct quotations, to preserve the accuracy of the quotation.
• American English uses -er endings for metric units: liter, kilometer; all other varieties of English, including Canadian, use -re: litre, kilometre.

Unit conversions

• Generally, conversions to and from metric units and US or imperial units should be provided, except:
  • When inserting a conversion would make a common expression awkward (The four-minute mile).
  • When units are part of the subject of a topic—nautical miles in articles about the history of nautical law, SI units in scientific articles, yards in articles about American football—it can be excessive to provide conversions every time a unit occurs. It could be best to note that this topic will use the units (possibly giving the conversion factor to another familiar unit in a parenthetical note or a footnote), and link the first occurrence of each unit but not give a conversion every time it occurs.
• Converted values should use a level of precision similar to that of the source value, so the Moon is 380,000 kilometres (240,000 mi) from Earth, not (236,121 mi). However, small numbers may need to be converted to a greater level of precision where rounding would cause a significant distortion, so one mile (1.6 km), not one mile (2 km).
• Category:Conversion templates can be used to convert and format many common units, including {{convert}}, which includes non-breaking spaces.
• In a direct quotation, always keep the source units.
  • Conversions required for units cited within direct quotations should appear within square brackets in the quote.
  • Alternatively, you can annotate an obscure use of units (e.g. five million board feet of lumber) with a footnote that provides conversion in standard modern units, rather than changing the text of the quotation. See the style guide for citation, footnoting and citing sources.
• Measurements should be accompanied by a proper citation of the source using a method described at the style guide for citation.
• Where footnoting or citing sources for values and units, identify both the source and the original units.

Avoiding ambiguities

• Identify and define ambiguous units on their first use in an article.
  • Avoid using unit abbreviations that have conflicting meanings in common units systems such as SI and US customary units:
    • Use nmi (or NM) to abbreviate nautical mile rather than nm (nanometre).
    • Use kn to abbreviate knot: kt could be confused with kilotonne; KN could be confused with kilonewton.
    • Link such units to their definitions on first use.
  • Some different units share the same name. These examples show the need to be specific.
    • Use nautical mile or statute mile rather than mile in nautical and aeronautical contexts.
    • Use long ton or short ton and not just ton; these units have no symbol or abbreviation and are always spelled out. The tonne, 1000 kilograms, is officially known as the metric ton in the US. Whichever name is used, the symbol is "t".
    • Use troy or avoirdupois ounce and not just ounce in articles about precious metals, black powder, and gemstones.
    • Use fluid ounce explicitly to avoid confusion with weight, and specify, if it is Imperial, US or other fluid ounce.
    • Use US or imperial gallon rather than just gallon (also with quarts, pints, and fluid ounces).
    • A calorie (symbol cal) refers to a gram calorie while the kilocalorie (symbol kcal) refers to the kilogram calorie (also known as small calorie and large calorie respectively). When used in a nutrition related article, use the kilocalorie as the primary unit. In U.S.-related articles, use the synonym dietary calorie with a one-time link to kilogram calorie.
  • For bits and bytes, specify whether the binary or decimal meaning of the prefixes kilo (k, K), mega (M), giga (G) and tera (T) is intended. See Quantities of bytes and bits.
• In tables and infoboxes, use unit symbols and abbreviations—do not spell them out.
• It may be appropriate to note that given quantities and conversions are approximate.
  • When part of a full sentence, write approximately in full (e.g., write Earth's radius is approximately 6,400 kilometres, not Earth's radius is approx. 6,400 kilometers or Earth's radius is ~ 6,400 kilometers).
  • In tables, infoboxes, or within brackets, use a tilde (~) or use approx. (e.g, write The capacity of a ship is sometimes expressed in gross register tons, a unit of volume defined as 100 cubic feet (~2.83 m³)).
  • Do not note a conversion as approximate where the initial quantity has already been noted as such, (e.g., write Earth's radius is approximately 6,400 km (4,000 mi), not Earth's radius is approximately 6,400 km (approx. 4,000 mi).

Unit names and symbols

Conventions

• Where space is limited, such as in tables, infoboxes, mathematical formulas, and parenthetical notes, unit symbols are preferable. In prose it is usually better to spell out unit names, but symbols may also be used when a unit (especially one with a very long name) is used many times in an article. However, spell out the first instance of each unit in an article: for example The typical batch is 250 kilograms ... and then 15 kg of emulsifier is added.
• If a unit symbol which can be unfamiliar to a general audience is used in an article, it should be shown parenthetically after the first use of the full unit name: for example, His initial betatron reached energies of 2.3 megaelectronvolts (MeV), while subsequent betatrons achieved 300 MeV.
• Values and unit symbols are always separated by a non-breaking space. (When they form a compound adjective, values and spelled out units should be separated by a hyphen.) The {{nowrap}} template or the &nbsp; character can be used for this purpose. For example, use 10 m or 29 kg, not 10m or 29kg.
  • Exceptions: Non-alphabetic symbols for degrees, minutes and seconds for angles and coordinates and the percent sign are unspaced (for example, 5° 24′ 21.12″ N for coordinates, 90° for an angle, 47% for a percentage, but 18 °C for a temperature). See also Manual of Style—Geographical Coordinates.
• Write unit symbols in upright roman type. (Italic type is normally reserved for variables and the like.) (e.g., 10 m or 29 kg, not 10 m or 29 kg).
• Standard symbols for units are undotted: e.g., m for the metre (not m.), kg for the kilogram (not kg.), in for the inch (not in., the quotation mark ", or the double prime ″), and ft for foot (not ft., the apostrophe ', or the prime ′).
  • Non-standard abbreviations should be dotted.
• Symbols have no plural form—an s is never appended (e.g., kg, km, in, lb, not kgs, kms, ins, lbs. Write bit, not bits unless bits is used as a word rather than a symbol).
• Unit names, even those named after people, are common nouns. They are not capitalized when written in full, except when a common noun takes a capital. Write The pascal is a unit of pressure, not The Pascal is a unit of pressure. In degree Celsius and degree Fahrenheit, the d is not usually capitalized, but the C and the F are (the common noun is degree, Celsius being a proper adjective).
• When unit names are combined by multiplication, separate them with a hyphen or space (e.g., newton-metre or newton metre). The plural is formed by pluralizing the last unit name (e.g., ten newton-metres).
• When unit names are combined by division, separate them with per (e.g., meter per second, not meter/second). The plural is formed by pluralizing the unit preceding the per, since it reads this many units of this per one unit of this (e.g., ten metres per second).
• When unit symbols are combined by multiplication, use a middle dot (·) or a non-breaking space ( ) to separate the symbols. For example, ms is the symbol for the millisecond, while m·s or m s is the symbol for the metre-second.
• When unit symbols are combined by division, use a slash to separate the symbols (e.g., for the metre per second use the symbol m/s, not mps) or use negative exponents (m·s⁻¹). Exceptions include "mph" for the mile per hour, "psi" for pounds per square inch, etc.
  • There should be no more than one slash per compound unit symbol, e.g., kg/(m·s), not kg/m/s or kg/m·s.
• Powers of unit symbols are expressed with a superscript exponent (write 5 km², not 5 km^2).
  • A superscript exponent indicates that the unit is raised to a power, not the unit and the quantity (3 metres squared is 9 square metres, or 9 m²).
  • For areas and volumes, squared and cubed US customary or imperial length units may instead be rendered with "sq" and "cu" between the number and the unit symbol (e.g., 15 sq mi and 3 cu ft, not 15 mi sq and 3 ft cu).
  • The symbols "sq" and "cu" are not used with BIPM-approved unit symbols.
  • Avoid the Unicode characters "²" and "³". They are harder to read on small displays, and are not aligned with superscript characters (see "x¹x²x³x⁴" vs. "x¹x²x³x⁴"). Instead, use superscript markup, created with .
• Numerical range of values are formatted as lower value-en dash-higher value-non breaking space-unit symbol (e.g., 5.9–6.3 kg, not 5.9 kg – 6.3 kg or 5.9 – 6.3 kg), or can be specified in written form using either unit symbol or unit names, and units can be stated either after both numerical values or after the last (e.g., from 5.9 to 6.3 kilograms, from 5.9 kilograms to 6.3 kilograms, from 5.9 to 6.3 kg and from 5.9 kg to 6.3 kg are all acceptable, but only one of these format should be in use in a given article).
• When dimensions are given, values each number should be followed by a unit name or symbol (e.g., write 1 m × 3 m × 6 m, not 1 × 3 × 6 m or 1 × 3 × 6 m³).

Units and symbols often written incorrectly

• The degree symbol is °. Using any other symbol (e.g., masculine ordinal º or ring above ˚) for this purpose is incorrect.
• The symbol for the bit is bit, not b. The byte may be represented by either one of the symbols B and byte, but not b or o (French octet). Unless explicitly stated otherwise, one byte is eight bits (see History of byte).
  • By extension, the symbols for the units of data rate kilobit per second, megabit per second and so on are kbit/s (not kbps or Kbps), Mbit/s (not Mbps or mbps), etc. Similarly, kilobyte per second and megabyte per second are kB/s (not kBps or KBps) and MB/s (not Mbps or MBps).
• The symbols for Celsius degrees, Fahrenheit degrees and kelvins are °C (not C), °F (not F), and K (not °K).
• For reasons of legibility, the preferred symbol for the unprefixed liter is upper-case L.
• If you need to express years as a unit, use the symbol a (from the Latin annum) along with SI prefixes (e.g., write The half life of thorium-230 is 77 ka and The Cambrian is a geologic period that dates from 540 Ma to 490 Ma).
  • There are many types of years (see year). When years are not used in the layman's meaning (e.g., Julie is 20 years old) clarify which type of year is meant.
• Roman prefixes are not used (M (10³), MM (10⁶), B (10⁹)). Use SI prefixes instead.

Quantities of bytes and bits

In quantities of bits and bytes, the prefixes kilo (abbreviated k or K), mega (M), giga (G), etc. are ambiguous. They may be based on a decimal system (like the standard SI prefixes), meaning 10³, 10⁶, 10⁹, etc., or they may be based on a binary system, meaning 1024 (2¹⁰), 1024², 1024³, etc. The binary meanings are more commonly used in relation to solid-state memory (such as RAM), while the decimal meanings are more common for data transmission rates and disk storage.

Multiple-byte units
Decimal Value Metric 1000 kB kilobyte 10002 MB megabyte 10003 GB gigabyte 10004 TB terabyte 10005 PB petabyte 10006 EB exabyte 10007 ZB zettabyte 10008 YB yottabyte 10009 RB ronnabyte 100010 QB quettabyte	Binary Value IEC Memory 1024 KiB kibibyte KB kilobyte 10242 MiB mebibyte MB megabyte 10243 GiB gibibyte GB gigabyte 10244 TiB tebibyte TB terabyte 10245 PiB pebibyte — 10246 EiB exbibyte — 10247 ZiB zebibyte — 10248 YiB yobibyte — — —
Orders of magnitude of data

The following recommendations are made for the use of these prefixes in Wikipedia articles:

• Editors should specify if the binary or decimal meanings of K, M, G, etc. are intended as the primary meaning. Consistency within each article is desirable, but the need for consistency may be balanced with other considerations.
  • The definition most relevant to the article should be chosen as primary one for that article (e.g., specify a binary definition in an article on RAM, decimal definition in an article on hard drives, and a binary definition for Windows file sizes, despite files usually being stored on hard drives).
  • Where consistency is not possible, specify wherever there is a deviation from the primary definition.
• Disambiguation should be shown in bytes or bits, with clear indication of whether in binary or decimal base. There is no preference in the way to indicate the number of bytes and bits, but the notation style should be consistent within an article. Acceptable examples include:

A 64 MB (64 × 1024² bytes) video card and a 100 GB (100 × 1000³ bytes) hard drive

A 64 MB (64 × 2²⁰ bytes) video card and a 100 GB (100×10⁹ bytes) hard drive

A 64 MB (67,108,864 bytes) video card and a 100 GB (100,000,000,000 bytes) hard drive

Avoid inconsistent combinations such as A 64 MB (67,108,864 bytes) video card and a 100 GB (100 × 1000³ bytes) hard drive. Footnotes, such as those seen in Power Macintosh 5500, may be used for disambiguation.

The IEC standard prefixes kibi-, mebi-, gibi-, etc. (symbols Ki, Mi, Gi, etc.) are not familiar to most Wikipedia readers, so are generally not to be used except under the following circumstances:

• when the article is on a topic where the majority of cited sources use the IEC prefixes,
• when directly quoting a source that uses the IEC prefixes,
• in articles specifically about or explicitly discussing the IEC prefixes.

Currencies

See also: Wikipedia:WikiProject Numismatics/Style § Article titles

Which one to use

• In country-specific articles, such as Economy of Australia, use the currency of the country.
• In non-country-specific articles such as Wealth, use US dollars (US$123), the dominant reserve currency of the world. Some editors also like to provide euro and/or pound sterling equivalents, formatted as described in the next section.

Formatting

• Fully identify a currency on its first appearance (AU$52); subsequent occurrences are normally given without the country identification or currency article link (just $88), unless this would be unclear. The exception to this is in articles related entirely to US- or UK-related topics, in which the first occurrence may also be shortened and not linked ($34 and £22, respectively), unless this would be unclear. Avoid over-identifying currencies that cannot be ambiguous; e.g., do not place EU or a similar prefix before the € sign.
• Do not place a currency symbol after the value (123$, 123£, 123€), unless the symbol is normally written as such. Do not write $US123 or $123 (US).
• Currency abbreviations that come before the number are unspaced if they consist of or end in a symbol (£123, €123), and spaced if alphabetic (R 75).
• If there is no common English abbreviation or symbol, use the ISO 4217 standard.
• Ranges are preferably formatted with one rather than two currency signifiers ($250–300, not $250–$300).
• Conversions of less familiar currencies may be provided in terms of more familiar currencies, such as the US dollar, euro or pound sterling. Conversions should be in parentheses after the original currency, rounding to the nearest whole unit, with at least the year given as a rough point of conversion rate reference; e.g., 1,000 Swiss francs (US$763 in 2005).
• For obsolete currencies, provide if possible an equivalent, formatted as a conversion, in the modern replacement currency (e.g. decimal pounds for historical pre-decimal pounds-and-shillings figures), or at least a US-dollar equivalent as a default in cases where there is no modern equivalent.
• When possible, always link the first occurrence of a symbol for lesser-known currencies (₮146); some editors consider it unnecessary to link the symbols of well-known currencies, but doing so can often be helpful to readers, as many countries use "dollars" or "pounds" as their base currency, and not all readers are familiar with the euro.
• The names of currencies, currency subdivisions, coins and banknotes should not be capitalised except where normal capitalisation rules require this (for example, at the start of a sentence).
• The pound sterling is represented by the £ symbol, with one horizontal bar. The double-barred ₤ symbol is ambiguous, as it has been used for Italian lire and other currencies as well as that of the British. For non-British currencies that use pounds or a pound symbol (e.g. the Irish pound, IR£) use the symbol conventionally preferred for that currency.

Common mathematical symbols

See also: Manual of Style (mathematics).

• For a negative sign or subtraction operator, use a minus sign (−). You can input a minus sign by either keying in &minus; or by clicking on it in the insert box beneath the edit window (located between the ± and × signs). Do not use an en dash (–), do not use a hyphen (-) unless writing code, and do not use an em dash (—).
• For a multiplication sign, use ×, which is input by clicking on it in the edit toolbox under the edit window or by keying in &times; (however, the letter x is accepted as a substitute for "by" in such terms as "4x4").

Common mathematical symbols

Name	Operation	Other use	Symbol	Wikicode	ASCII	Unicode	As binary operator (e.g. 1 + 1)	As unary operator (e.g. +1)
Plus sign	Addition	Positive sign	+	+	+	U+002B	Spaced	Unspaced
Plus or minus	Addition or subtraction	Positive or negative sign	±	±	±	U+00B1	Spaced	Unspaced
Minus or plus	Subtraction or addition	Negative or positive sign	∓	—	∓	U+2213	Spaced	Unspaced
Minus sign	Subtraction	Negative sign	−	−	−	U+2212	Spaced	Unspaced
Multiplication sign, cross	Multiplication, vector product	—	×	×	×	U+00D7	Spaced	—
Division sign, obelus	Division	—	÷	÷	÷	U+00F7	Spaced	—
Equal sign	Equation	—	=	—	=	U+003D	Spaced	—
Not equal sign	Non-equation	—	≠	≠	≠	U+2260	Spaced	—
Approximate sign	Approximation	—	≈	≈	≈	U+2248	Spaced	—
Less than sign	Inequation	—	<	&lt;	&#60;	U+3C	Spaced	—
Less than or equal to	Inequation	—	≤	&le;	&#8804;	U+2264	Spaced	—
Greater than sign	Inequation	—	>	&gt;	&#62;	U+3E	Spaced	—
Greater than or equal to	Inequation	—	≥	&ge;	&#8805;	U+2265	Spaced	—

Unnecessary vagueness

Use accurate measurements whenever possible.

Vague	Precise
The wallaby is small	The average male wallaby is 1.6 metres (63 in) from head to tail.
Prochlorococcus marinus is a tiny cyanobacterium.	The cyanobacterium Prochlorococcus marinus is 0.5 to 0.8 micrometre across.
The large oil spill stretched a long way down the Alaskan coast.	The oil spill that drifted down the Alaskan coast was 3 statute miles (5 km) long and 1,000 feet (300 m) wide.
A beautiful little house in Malibu	A $400,000 residential property in Malibu

Geographical coordinates

For draft guidance on, and examples of, coordinates for linear features, see Wikipedia:WikiProject Geographical coordinates/Linear.

Quick guide:

Quick how-to

To add 57°18′22″N 4°27′32″W to the top of an article, use {{Coord}}, thus:

{{Coord|57|18|22|N|4|27|32|W|display=title}}

These coordinates are in degrees, minutes, and seconds of arc.

"title" means that the coordinates will be displayed next to the article's title at the top of the page (in desktop view only; title coordinates do not display in mobile view) and before any other text or images. It also records the coordinates as the primary location of the page's subject in Wikipedia's geosearch API.

To add 44.1124°N 87.9130°W / 44.1124; -87.9130 to the top of an article, use either

{{Coord|44.1124|N|87.9130|W|display=title}}

(which does not require minutes or seconds but does require the user to specify north/ south and east/west) or

{{Coord|44.1124|-87.9130|display=title}}

(in which the north and east are presumed by positive values while the south and west are negative ones). These coordinates are in decimal degrees.

• Degrees, minutes and seconds, when used, must each be separated by a pipe ("|").
• Map datum must be WGS84 if possible (except for off-Earth bodies).
• Avoid excessive precision (0.0001° is <11 m, 1″ is <31 m).
• Maintain consistency of decimal places or minutes/seconds between latitude and longitude.
• Latitude (N/S) must appear before longitude (E/W).

Optional coordinate parameters follow the longitude and are separated by an underscore ("_"):

• dim: dim:N (viewing diameter in metres)
• region: region:R (ISO 3166-1 alpha-2 or ISO 3166-2 code)
• type: type:T (landmark or city(30,000), for example)

Other optional parameters are separated by a pipe ("|"):

• display

  |display=inline (the default) to display in the body of the article only,

  |display=title to display at the top of the article only (in desktop view only; title coordinates do not display in mobile view), or

  |display=inline,title to display in both places.

• name

  name=X to label the place on maps (default is PAGENAME)

Thus: {{Coord|44.1172|-87.9135|dim:30_region:US-WI_type:event

|display=inline,title|name=accident site}}

Use |display=title (or |display=inline,title) once per article, for the subject of the article, where appropriate.

• Per WP:ORDER, the template is placed at the bottom of the article in the 'end matter', after any navigation templates, but before all categories, including the {{DEFAULTSORT}} template. The {{coord}} template may also be placed within an infobox, instead of at the bottom of the article.
• For full details, refer to {{Coord/doc}}.
• Additional guidance is available at obtaining coordinates and converting coordinates.

Geographical coordinates on Earth should be entered using a template to standardize the format and to provide a link to maps of the coordinates. As long as the templates are adhered to, a robot performs the functions automatically.

First, obtain the coordinates. Please don't be overly precise.

Two types of template are available:

• {{coord}}, which has replaced the coor family (and combined their functionality), offers users a choice of display format through user styles, emits a Geo microformat, and is supported by Google Earth.
• Infoboxes such as {{Infobox settlement}}

Depending on the form of the coordinates, the following formats are available.

For just degrees (including decimal values):

{{coord|dd|N/S|dd|E/W}}

For degrees/minutes:

{{coord|dd|mm|N/S|dd|mm|E/W}}

For degrees/minutes/seconds:

{{coord|dd|mm|ss|N/S|dd|mm|ss|E/W}}

where:

• DD, MM, SS are the degrees, minutes, seconds, listed in sequence
• N/S is either N or S, depending on which hemisphere, and
• E/W is either E or W, depending on which hemisphere
• negative values may be used in lieu of S and W

For example:

The city of Oslo, located at 59° 55′ N, 10° 44′ E, enter:

{{coord|59|55|N|10|44|E}} — which becomes 59°55′N 10°44′E

A country, like Botswana, less precision is appropriate:

{{coord|22|S|24|E}} — which becomes 22°S 24°E

Higher levels of precision are obtained by using seconds

{{coord|33|56|24|N|118|24|00|W}} — which becomes 33°56′24″N 118°24′00″W

Coordinates can be entered as decimal values

{{coord|33.94|S|118.40|W}} — which becomes 33.94°S 118.40°W / -33.94; -118.40

Increasing or decreasing the number of decimal places can control the precision. Trailing zeroes should be included.

London Heathrow Airport, Amsterdam, Jan Mayen and Mount Baker are examples of articles that contain geographical coordinates.

Generally, the larger the object being mapped, the less precise the coordinates should be. For example, if just giving the location of a city, precision greater than 100 meters is not needed unless specifying a particular point in the city, for example the central administrative building. Specific buildings or other objects of similar size would justify precisions down to 10 meters or even one meter in some cases (1′′ ~15 m to 30 m, 0.0001° ~5.6 m to 10 m).

The final field, following the E/W, is available for specification of attributes, such as type, region and scale.

When you have added the coordinates, you might want to remove the {{coord missing}} tag from the article, if present.

For more information, see the geographical coordinates WikiProject.

Templates other than {{coord}} should use the following variables for coordinates: lat_d, lat_m, lat_s, lat_NS, long_d, long_m, long_s, long_EW.

See also

• For page naming specifics, see Wikipedia:Naming conventions (numbers and dates).
• m:Help:Date formatting feature at Meta
• Displaying numbers and numeric expressions

Notes

Longer periods

• Months are expressed as whole words (February, not 2), except in the ISO 8601 format; unlike in some other languages, names of months (and of days of the week) are capitalized in English. Abbreviations such as Feb are used only where space is extremely limited, such as in tables and infoboxes. Do not insert of between a month and a year (April 2000, not April of 2000).
• Seasons. Because the seasons are not simply reversed in each hemisphere – and areas near the equator tend to have just wet and dry seasons – neutral wording may be preferable (in early 1990, in the second quarter of 2003, around September). Use a date or month rather than a season name, unless there is a logical connection (the autumn harvest). Seasons are normally spelled with a lower-case initial.
• Years
  • Years are normally expressed in digits. Avoid inserting the words the year before the digits (1995, not the year 1995), unless the meaning would otherwise be unclear.
  • Year ranges, like all ranges, are separated by an en dash, not a hyphen or slash: 2005–06 is a two-year range, whereas 2005/06 is a period of twelve months or less such as a sports season or a financial year. A closing CE/AD year is normally written with two digits (1881–86) unless it is in a different century from that of the opening year (1881–1986). The full closing year is acceptable, but abbreviating it to a single digit (1881–6) or three digits (1881–886) is not. A closing BCE or BC year is given in full (2590–2550 BCE). While one era signifier at the end of a date range requires an unspaced en dash (12–5 BC), a spaced en dash is required when a signifier is used after the opening and closing years (5 BC – AD 29).
  • To indicate around/approximately/about, the abbreviations c. and ca. are preferred over circa, approximately or approx., and are spaced (c. 1291). Do not use a question mark for this function (1291?), as this may imply to the reader an uncertainty on the part of Wikipedia editors rather than on the part of reliable historians.
• Decades
  • Decades as such contain no apostrophe (the 1980s, not the 1980's). The two-digit form is never used in reference to the decade as a time span per se.
  • The two-digit style, to which a preceding apostrophe is typically added, is used only in reference to a social era or cultural phenomenon that roughly corresponds to and is said to define a decade, and only if it is used in a sourceable stock phrase (the Roaring '20s, the Gay '90s), or when there is a notable connection between the period and what is being discussed in the sentence (a sense of social justice informed by '60s counterculture, but grew up in 1960s Boston, moving to Dallas in 1971). Such an abbreviation should not be used if it would be redundant ('80s Reaganomics) or if it does not have a clear cultural significance and usage (the '10s).
• Centuries and millennia
  • For purposes of written style, the English Wikipedia does not recognize a year 0. Therefore, for dates AD (or CE) the 1st century was 1–100, the 17th century was 1601–1700, and the second millennium was 1001–2000; for dates BC (or BCE) the 1st century was 100–1; the 17th century was 1700–1601, and the second millennium was 2000–1001.
  • Forms such as the 1700s are normally best avoided (although the difference in meaning should be noted: the 1700s is 1700–1799, whereas the 18th century is 1701–1800).

Year numbering systems

• Years are numbered according to the traditional western Dionysian era ("Common Era").
  • AD and BC are the traditional ways of referring to these eras. However, the CE and BCE is becoming more common in academic and some religious writing. No preference is given to either style.
    • Do not use CE or AD unless the date would be ambiguous without it. e.g. "The Norman Conquest took place in 1066." not 1066 CE or AD 1066.
    • BCE and CE or BC and AD are written, in upper case, spaced, and without periods (full stops).
    • Use either the BC-AD or the BCE-CE notation, but not both in the same article. AD may appear before or after a year (AD 106, 106 AD); the other abbreviations appear after (106 CE, 3700 BCE, 3700 BC).
    • Do not change from one style to another unless there is substantial reason for the change, and consensus for the change with other editors.
• Uncalibrated (bce) radiocarbon dates: Some source materials will indicate whether a date is calibrated or not simply by a change in capitalization; this is often a source of confusion for the unwary reader. Do not give uncalibrated radiocarbon dates (represented by the lower-case bce unit, occasionally bc or b.c. in some sources), except in directly quoted material, and even then include a footnote, a square-bracketed editor's note [like this], or other indication to the reader what the calibrated date is, or at least that the date is uncalibrated. Calibrated and uncalibrated dates can diverge surprisingly widely, and the average reader does not recognize the distinction between bce and BCE / BC.
• Abbreviations indicating long periods of time ago—such as BP (before present), as well as various annum-based units such as ka (kiloannum), Ma (megaannum) and Ga (gigaannum) are given as full words on first occurrence. Where source quotations use the abbreviations kya (thousand years ago), mya (million years ago), or bya (billion years ago) this should be explained to the reader, as in "a measured Libby radiocarbon date of 35.1 mya [million years ago] had to be calibrated ..." The kya, mya and bya symbols are deprecated in some fields such as geophysics and geology, but remain common in others, such as anthropology.
  • BP: Do not convert other notations to BP unless you are certain of what you are doing. In some contexts the unit BP is actually defined as "years before January 1, 1950", not "years before the literal present", and the conversion may introduce an error if the date being converted is not a wide approximation (18,000 BP) but a more narrow one or an actual known year. BP years are given as 18,000 BP or spelled out as 18,000 years before present (not 18,000 YBP, 18,000 before present, 18,000 years before the present, or similar.)

Calendars

See also: Old Style and New Style dates

Dates can be given in any appropriate calendar, as long as the date in either the Julian or Gregorian calendars is provided, as described below. For example, an article on the early history of Islam may give dates in both Islamic and Julian calendars. Where a calendar other than the Julian or Gregorian is used, this must be clear to readers.

• Current events are given in the Gregorian calendar.
• Dates before the adoption of the Gregorian calendar on 15 October 1582 are normally given in the Julian calendar. The Julian day and month should not be converted to the Gregorian calendar, but the start of the Julian year should be assumed to be 1 January (see below for more details).
• Dates for Roman history before 45 BC are given in the Roman calendar, which was neither Julian nor Gregorian. When (rarely) the Julian equivalent is certain, it may be included.
• The Julian or Gregorian equivalent of dates in early Egyptian and Mesopotamian history is often debatable. Follow the consensus of reliable sources, or indicate their divergence.
• Dates of events in countries using the Gregorian calendar are given in the Gregorian calendar. This includes some of the Continent of Europe from 1582, the British Empire from 14 September 1752, and Russia from 14 February 1918 (see the Gregorian calendar article).

The dating method used in a Wikipedia article should follow that used by reliable secondary sources. If the reliable secondary sources disagree, choose the most common used by reliable secondary sources and note the usage in a footnote.

At some places and times, dates other than 1 January were used as the start of the year. The most common English-language convention was the Annunciation Style used in Britain and its colonies, in which the year started on 25 March, Annunciation Day; see the New Year article for a list of other styles. 1 January is assumed to be the opening date for years; if there is reason to use another start-date, this should be stated.

If there is a need to mention Old Style or New Style dates in an article (as in the Glorious Revolution), a footnote should be provided on the first usage, stating whether the "New Style" refers to a start of year adjustment or to the Gregorian calendar (it can mean either).

Time zones

When writing a date, first consider where the event happened and use the time zone there. For example, the date of the Attack on Pearl Harbor should be December 7, 1941 (Hawaii time/date). If it is difficult to judge where, consider what is significant. For example, if a vandal based in Japan attacked a Pentagon computer in the US, use the time zone for the Pentagon, where the attack had its effect. If known, include the UTC date and time of the event in the article, indicating that it is UTC.

Numbers

Numbers as figures or words

As a general rule, in the body of an article, single-digit whole numbers from zero to nine are spelled out in words; numbers greater than nine are commonly rendered in numerals, or may be rendered in words if they are expressed in one or two words (16 or sixteen, 84 or eighty-four, 200 or two hundred, but 3.75, 544, 21 million). This applies to ordinal numbers as well as cardinal numbers. However there are frequent exceptions to these rules.

• In tables and infoboxes, quantitative data is expressed as numerals; numerals will also fit better in limited space. Numbers within a table's explanatory text and comments should be consistent with the general rule.
• Comparable quantities should be all spelled out or all figures: we may write either 5 cats and 32 dogs or five cats and thirty-two dogs, not five cats and 32 dogs.
• Adjacent quantities which are not comparable should usually be in different formats: twelve 90-minute volumes or 12 ninety-minute volumes is more readable than 12 90-minute volumes or twelve ninety-minute volumes.
• Numbers that begin a sentence are spelled out, since using figures risks the period being read as a decimal point or abbreviation mark; it is often better to recast the sentence than to simply change format, which may produce other problems: e.g., do not use Nineteen forty five and 1950 were important elections for the Labour Party, but rather The elections of 1945 and 1950 were important for the Labour Party.
• The numerical elements of dates and times are not normally spelled out (that is, do not use the seventh of January or twelve forty-five p.m. or Two thousand eight was the year that ... ). However, they should be spelled out where customary in historical references such as Seventh of March Speech and Fifth of November; these are treated as proper names.
• Centuries are named in figures: (the 5th century CE; 19th-century painting); when the adjective is hyphenated, consider nineteenth-century painting, but not when contrasted with painting in the 20th century.
• Simple fractions are normally spelled out; use the fraction form if they occur in a percentage or with an abbreviated unit (1⁄8 mm or an eighth of a millimeter, but not an eighth of a mm) or if they are mixed with whole numerals.
• Decimal representations containing a decimal point are not spelled out (1.00, 3.14159).
• Numbers in mathematical formulae are never spelled out ("3 < π < 22/7", not "three < π < 22 sevenths").
• Do not use spelled-out numbers before symbols for units of measurement: write five minutes, 5 minutes, or 5 min, but not five min.
• Measurements, stock prices, and other quasi-continuous quantities are normally stated in figures, even when the value is a small positive integer: 9 mm, The option price fell to 5 within three hours after the announcement.
• When expressing large approximate quantities, it is preferable to write them spelled out, or partly in figures and part as a spelled‑out named number; e.g., one hundred thousand troops may be preferable to 100,000 troops when the size of the force is not known exactly; write Japan has the world's tenth largest population, with about 128 million people (as it is just an approximation to a number likely to be anywhere between 127,500,000 and 128,500,000), but The movie grossed $28,106,731 on its opening day (the exact quantity).
• When both a figure and spelled-out named number are used in a quantity, it is useful to use a non-breaking space, as in 128 million or 128{{nbsp}}million to prevent a line break from occurring between them.
• Sometimes figures and words may carry different meanings, for example Every number except one implies that there is one exception (we don't know which), while Every number except 1 means that the specific number 1 is the exception.
• Proper names, formal numerical designations, and other idioms comply with common usage: e.g., write Chanel No. 5, 4 Main Street, 1-Naphthylamine, Channel 6, Fourth Amendment, Seventeenth Judicial District, Seven Years' War. This is the case even where it causes a numeral to open a sentence, although this is usually avoided by rewording.

Typography

• Spelled-out two-word numbers from 21 to 99 are hyphenated (fifty-six), as are fractions (seven-eighths). Do not hyphenate other multi-word numbers (five hundred, not five-hundred).
• Where a whole number in a percentage is spelled out, the percent sign is not used (three percent or 3%, not three %).
• The ordinal suffix (e.g., th) is not superscripted (23rd and 496th, not 23^rd and 496^th).

Large numbers

See also: Order of magnitude and Long and short scales

• In a number with many digits, digit grouping symbols (inserted at intervals from the decimal point) should be used to subdivide the number into easily readable groups. The acceptable digit grouping schemes are:
  • Commas every three digits to the left of the decimal point, and no grouping to the right of the decimal point (e.g. 8,274,527 or 0.12345). This is traditional usage in many English-language contexts.
  • Thin, non-breaking spaces every three digits (e.g. 8274527 or 0.12345). This format is suggested in BIPM and NIST style guides for scientific and engineering works, and is in common use in interlanguage contexts. The {{gaps}} template uses CSS to produce this output (using the syntax {{gaps|8|274|527}}). Using HTML entities for this purpose (e.g.   or  ) may cause rendering problems in some browsers, and should be avoided when practical.
  • Other traditional digit grouping schemes, when relevant to the subject matter of the article (e.g. 82,74,527 in the Indian numbering system, or 3.141592653589793238462643383279… for long truncated representations of mathematical constants).
  • When a number has exactly four digits on any side of the decimal separator, those digits may optionally be expressed as a group of four instead of three (e.g. both 9876 and 9,876 are acceptable, although commas or spaces are not used in four-digit years, page numbers, and addresses).
• Large round numbers are generally assumed to be approximations; only where the approximation could be misleading is it necessary to qualify with words such as "about".
• Avoid overly precise values where they are unlikely to be stable or accurate, or where the precision is unnecessary in the context. The sentence The speed of light in a vacuum is 299,792,458 metres per second may well be appropriate since it is defined as precisely that value; The distance from the Earth to the Sun is 149,014,769 kilometres and The population of Cape Town is 2,968,790 people would usually not be, because both values are unstable at that level of precision, and readers are unlikely to care in the context.
• Scientific notation, e.g. 5.8×10⁷ kg, is preferred in scientific contexts; editors can use the {{val}} template, which generates such expressions with the syntax {{val|5.8|e=7|u=kg}}.
• Where values in the millions occur a number of times through an article, upper-case "M" may be used for "million", unspaced, after spelling out the first occurrence, e.g. She bequeathed her fortune of £100 million unequally: her eldest daughter received £70M, her husband £18M, and her three sons £4M each.
• The named numbers, billion and trillion are understood to be “short scale”, 10⁹ and 10¹², respectively (see Long and short scales). After the first occurrence in an article, "billion" may be abbreviated to unspaced "bn" ($35bn).

Fractions

The template {{frac}} is available for representing common fractions. For p⁄q, type {{frac|p|q}}. For N+p⁄q, type {{frac|N|p|q}}. When copied and pasted, the latter text will appear as N+p/q.

Decimal points

• A decimal point is used between the integer and the fractional parts of a decimal; a comma is never used in this role (6.57, not 6,57).
• The number of decimal places should be consistent within a list or context (The response rates were 41.0 and 47.4 percent, respectively, not The response rates were 41 and 47.4 percent, respectively).
• Numbers between −1 and +1 require a leading zero (0.02, not .02); exceptions are sporting performance averages (.430 batting average) and commonly used terms such as .22 caliber.

Percentages

• Percent or per cent are commonly used to indicate percentages in the body of an article. The symbol % is more common in scientific or technical articles and in complex listings.
• The symbol is unspaced (71%, not 71 %).
• In tables and infoboxes, the symbol % is normally preferred to the spelled-out percent or per cent.
• Ranges are preferably formatted with one rather than two percentage signifiers (22–28%, not 22%–28%).
• Avoid ambiguity in expressing a change of rates. This can be done by using percentage points, not percentages, to express a change in a percentage or the difference between two percentages; for example, "The agent raised the commission by five percentage points, from 10 to 15%" (if the 10% commission had instead been raised by 5%, the new rate would have been 10.5%). It is often possible to recast the sentence to avoid the ambiguity ("made the commission larger by half."). Percentage point should not be confused with basis point, which is a hundredth of a percentage point.

Natural numbers

The set of natural numbers has two common meanings: {0, 1, 2, 3, ...}, which may also be called non-negative integers, and {1, 2, 3, ...}, which may also be called positive integers. Use the sense appropriate to the field to which the subject of the article belongs if the field has a preferred convention. If the sense is unclear, and if it is important whether or not zero is included, consider using one of the alternative phrases rather than natural numbers if the context permits.

Repeating decimals

The preferred way to indicate a repeating decimal is to place a bar over the digits that repeat. To achieve this the template {{overline}} can be used. For example, the markup 14.{{overline|285714}} gives "14.285714".

Consider a short explanation of the notation the first time this notation is used in an article. Some authors place the repeating digits in parentheses rather than using an overbar (perhaps because overbars are not available in their typesetting environment) but this should be avoided in Wikipedia to avoid confusion with expressing uncertainty.

Non-base-10 notations

For numbers expressed in bases other than base ten:

• In computer-related articles, use the C programming language prefixes 0x (zero-ex) for hexadecimal and 0 (zero) for octal. For binary, use 0b. Consider including a note at the top of the page about these prefixes.
• In all other articles, use subscript notation. For example: 137₉, 241₆, 2A9₁₂, A87D₁₆ (use <sub> and </sub>).
• For base eleven and higher, use whatever symbols are conventional for that base. One quite common convention, especially for base 16, is to use upper-case A–F for digits from 10 through 15 (0x5AB3).

Scientific notation, engineering notation, and uncertainty

Notations

• The template {{val}} can be used to facilitate the generation of scientific notation. It is a flexible tool that allows editors great latitude and must have arguments (each section between the vertical bars) properly entered in order for it to generate output that is compliant with formating conventions.
• Scientific notation is done in the format of one leading digit/decimal marker/rest of digits/×10ⁿ, where n is the integer that gives one leading digit.
  • 1.602×10⁻¹⁹ is a proper use of scientific notation.
  • 160.2×10⁻¹⁷ is not a proper use of scientific notation.
• Engineering notation is done in the format of leading digits/decimal marker/rest of digits/×10ⁿ, where n is a multiple of 3. The number of leading digits is adjusted accordingly.
  • 132.23×10⁶ is a proper use of engineering notation.
  • 1.3223×10⁸ is a not proper use of engineering notation.
• It is clearer to avoid mixing scientific notation and engineering notation in the same context (e.g., do not write A 2.23×10² m² region covered by 234.0×10⁶ grains of sand).
• Use discretion when it comes to using scientific and engineering notation. Not all values need to be written in it.
  • Sometimes it is useful to compare values with the same power of 10 (often in tables) and scientific or engineering notation might not be appropriate.

Uncertainty

• Uncertainties can be written in various ways:
  • Value/±/uncertainty/×/10ⁿ/unit symbol (e.g., (1.534±0.35)×10²³ m)
    • Do not group value and uncertainty in parenthesis before the multiplier (e.g., do not write (15.34 ± 0.35) × 10²³ m)
  • Value/superscript positive uncertainty/subscript negative uncertainty/×/10ⁿ/unit symbol (e.g., 15.34+0.43
    −0.23×10²³ m)
  • Value(uncertainty in the last digits)/×/10ⁿ/unit symbol (e.g., 1.604(48)×10⁻⁴ J)
  • Value/±/relative uncertainty(percent)/unit symbol (e.g., 12.34 ± 5% m²)
• The template {{val}} may be used to automatically handle all of this.

Units of measurement

The use of units of measurement is based on the following principles:

• Avoid ambiguity: Aim to write so you cannot be misunderstood.
• Familiarity: The less readers have to look up definitions, the easier it is to be understood.
• International scope: Wikipedia is not country-specific; apart from region-specific topics, use internationally accepted units for the topic at hand.

If there is trouble balancing these bullets, consult other editors through the talk page and try to reach consensus.

Adopting suggestions from standards bodies: You might wonder why Wikipedia’s style guides have not always adopted the suggestions of internationally recognized standards bodies. The objective of any encyclopedia is to communicate to its readership with minimal confusion. Sometimes, real-world practices do not follow the suggestions of standards bodies such as the BIPM and their SI, the IEC, and the ISO. When that occurs, Wikipedia typically follows the real‑world practice so our articles read naturally and there is minimal confusion.

For instance, the real world—and therefore Wikipedia too—flouts SI writing style regarding the percent (%) symbol. According to the BIPM’s SI brochure: Subsection 5.3.3, Formatting the value of a quantity, a space is always used to separate the unit symbol from the numeric value. Notable exceptions are the unit symbols for degree, minute, and second for plane angle, °, ′, and ″ (e.g., a latitude of 47° 38′ 8.8″). However, according to their SI brochure: 5.3.7 Stating values of dimensionless quantities, or quantities of dimension one, the exception does not apply to the “%” symbol; it states as follows: “When it [the percent symbol] is used, a space separates the number and the symbol %.” This practice has not been well adopted with regard to the % symbol, is contrary to Wikipedia’s Manual of Style, and editors are asked to abide by this style guide so that our articles read most naturally. It is 50%, not 50 %.

Wikipedia similarly follows real-world practices with the binary prefixes (megabyte, kilobyte) and their unit symbols (MB and KB respectively). This practice ignores the fact that the IEC in 1998 proposed new binary prefixes for the world to adopt. Their proposal introduced new units of measure like mebibyte (symbol: MiB) and kibibyte (symbol: KiB). Again, consistent with our objective of communicating to our readership with minimal confusion, Wikipedia follows the real‑world practice observed by the computing world when they communicate to a general‑interest audience. It is 256 MB of RAM, not 256 MiB of RAM. In order to communicate with minimal confusion to its readership, Wikipedia follows real‑world practices and does not endeavor to promote change by attempting to lead by example.

Which units to use

• In articles which are not region-specific, prefer internationally accepted units. Usually, they are the units of the International System of Units (SI) and non-SI units accepted for use with SI; but there are various exceptions for particular classes of measurements. However:
  • in US-specific topics, the primary units are generally US customary units, with conversions given into SI and related units;
  • UK-related topics may have either SI or imperial units as the primary units.
• Generally, use units consistently (e.g., write a 10-kilogram (22 lb) bag of potatoes and a 5 kg (11 lb) bag of carrots, not a 10-kilogram (22 lb) bag of potatoes and a 11-pound (5 kg) bag of carrots).
  • Nominal and defined values should be given in the original units first, even if this makes the article inconsistent: for example, When the Republic of Ireland adopted the metric system, the road speed limit in built-up areas was changed from 30 miles per hour (48 km/h) to 50 kilometres per hour (31 mph). (The focus is on the change of units, not on the 3.6% increase.)
• If editors cannot agree on the sequence of units, put the source value first and the converted value second. If the choice of units is arbitrary, use SI units as the main unit, with converted units in parentheses.
• Use familiar units rather than obscure units—do not write over the heads of the readership (e.g., a general interest topic such as black holes would best be served by having mass expressed in solar masses, but it might be appropriate to use Planck units in an article on the mathematics of black hole evaporation).
• Some disciplines use units not approved by the BIPM, or write them differently from BIPM-prescribed format. When a clear majority of the sources relevant to those disciplines use such units, articles should follow this (e.g., using cc in automotive articles and not cm³). Such use of non-standard units are always linked on first use.
• In scientific articles, use the units employed in the current scientific literature on that topic. This will usually be SI, but not always; for example, natural units are often used in relativistic and quantum physics, and Hubble's constant should be quoted in its most common unit of (km/s)/Mpc rather than its SI unit of s⁻¹.
• Avoid ambiguous unit names (e.g., write imperial gallon or US gallon rather than gallon). Only in the rarest of instances should ambiguous units be used, such as in direct quotations, to preserve the accuracy of the quotation.
• American English uses -er endings for metric units: liter, kilometer; all other varieties of English, including Canadian, use -re: litre, kilometre.

Unit conversions

• Generally, conversions to and from metric units and US or imperial units should be provided, except:
  • When inserting a conversion would make a common expression awkward (The four-minute mile).
  • When units are part of the subject of a topic—nautical miles in articles about the history of nautical law, SI units in scientific articles, yards in articles about American football—it can be excessive to provide conversions every time a unit occurs. It could be best to note that this topic will use the units (possibly giving the conversion factor to another familiar unit in a parenthetical note or a footnote), and link the first occurrence of each unit but not give a conversion every time it occurs.
• Converted values should use a level of precision similar to that of the source value, so the Moon is 380,000 kilometres (240,000 mi) from Earth, not (236,121 mi). However, small numbers may need to be converted to a greater level of precision where rounding would cause a significant distortion, so one mile (1.6 km), not one mile (2 km).
• Category:Conversion templates can be used to convert and format many common units, including {{convert}}, which includes non-breaking spaces.
• In a direct quotation, always keep the source units.
  • Conversions required for units cited within direct quotations should appear within square brackets in the quote.
  • Alternatively, you can annotate an obscure use of units (e.g. five million board feet of lumber) with a footnote that provides conversion in standard modern units, rather than changing the text of the quotation. See the style guide for citation, footnoting and citing sources.
• Measurements should be accompanied by a proper citation of the source using a method described at the style guide for citation.
• Where footnoting or citing sources for values and units, identify both the source and the original units.

Avoiding ambiguities

• Identify and define ambiguous units on their first use in an article.
  • Avoid using unit abbreviations that have conflicting meanings in common units systems such as SI and US customary units:
    • Use nmi (or NM) to abbreviate nautical mile rather than nm (nanometre).
    • Use kn to abbreviate knot: kt could be confused with kilotonne; KN could be confused with kilonewton.
    • Link such units to their definitions on first use.
  • Some different units share the same name. These examples show the need to be specific.
    • Use nautical mile or statute mile rather than mile in nautical and aeronautical contexts.
    • Use long ton or short ton and not just ton; these units have no symbol or abbreviation and are always spelled out. The tonne, 1000 kilograms, is officially known as the metric ton in the US. Whichever name is used, the symbol is "t".
    • Use troy or avoirdupois ounce and not just ounce in articles about precious metals, black powder, and gemstones.
    • Use fluid ounce explicitly to avoid confusion with weight, and specify, if it is Imperial, US or other fluid ounce.
    • Use US or imperial gallon rather than just gallon (also with quarts, pints, and fluid ounces).
    • A calorie (symbol cal) refers to a gram calorie while the kilocalorie (symbol kcal) refers to the kilogram calorie (also known as small calorie and large calorie respectively). When used in a nutrition related article, use the kilocalorie as the primary unit. In U.S.-related articles, use the synonym dietary calorie with a one-time link to kilogram calorie.
  • For bits and bytes, specify whether the binary or decimal meaning of the prefixes kilo (k, K), mega (M), giga (G) and tera (T) is intended. See Quantities of bytes and bits.
• In tables and infoboxes, use unit symbols and abbreviations—do not spell them out.
• It may be appropriate to note that given quantities and conversions are approximate.
  • When part of a full sentence, write approximately in full (e.g., write Earth's radius is approximately 6,400 kilometres, not Earth's radius is approx. 6,400 kilometers or Earth's radius is ~ 6,400 kilometers).
  • In tables, infoboxes, or within brackets, use a tilde (~) or use approx. (e.g, write The capacity of a ship is sometimes expressed in gross register tons, a unit of volume defined as 100 cubic feet (~2.83 m³)).
  • Do not note a conversion as approximate where the initial quantity has already been noted as such, (e.g., write Earth's radius is approximately 6,400 km (4,000 mi), not Earth's radius is approximately 6,400 km (approx. 4,000 mi).

Unit names and symbols

Conventions

• Where space is limited, such as in tables, infoboxes, mathematical formulas, and parenthetical notes, unit symbols are preferable. In prose it is usually better to spell out unit names, but symbols may also be used when a unit (especially one with a very long name) is used many times in an article. However, spell out the first instance of each unit in an article: for example The typical batch is 250 kilograms ... and then 15 kg of emulsifier is added.
• If a unit symbol which can be unfamiliar to a general audience is used in an article, it should be shown parenthetically after the first use of the full unit name: for example, His initial betatron reached energies of 2.3 megaelectronvolts (MeV), while subsequent betatrons achieved 300 MeV.
• Values and unit symbols are always separated by a non-breaking space. (When they form a compound adjective, values and spelled out units should be separated by a hyphen.) The {{nowrap}} template or the &nbsp; character can be used for this purpose. For example, use 10 m or 29 kg, not 10m or 29kg.
  • Exceptions: Non-alphabetic symbols for degrees, minutes and seconds for angles and coordinates and the percent sign are unspaced (for example, 5° 24′ 21.12″ N for coordinates, 90° for an angle, 47% for a percentage, but 18 °C for a temperature). See also Manual of Style—Geographical Coordinates.
• Write unit symbols in upright roman type. (Italic type is normally reserved for variables and the like.) (e.g., 10 m or 29 kg, not 10 m or 29 kg).
• Standard symbols for units are undotted: e.g., m for the metre (not m.), kg for the kilogram (not kg.), in for the inch (not in., the quotation mark ", or the double prime ″), and ft for foot (not ft., the apostrophe ', or the prime ′).
  • Non-standard abbreviations should be dotted.
• Symbols have no plural form—an s is never appended (e.g., kg, km, in, lb, not kgs, kms, ins, lbs. Write bit, not bits unless bits is used as a word rather than a symbol).
• Unit names, even those named after people, are common nouns. They are not capitalized when written in full, except when a common noun takes a capital. Write The pascal is a unit of pressure, not The Pascal is a unit of pressure. In degree Celsius and degree Fahrenheit, the d is not usually capitalized, but the C and the F are (the common noun is degree, Celsius being a proper adjective).
• When unit names are combined by multiplication, separate them with a hyphen or space (e.g., newton-metre or newton metre). The plural is formed by pluralizing the last unit name (e.g., ten newton-metres).
• When unit names are combined by division, separate them with per (e.g., meter per second, not meter/second). The plural is formed by pluralizing the unit preceding the per, since it reads this many units of this per one unit of this (e.g., ten metres per second).
• When unit symbols are combined by multiplication, use a middle dot (·) or a non-breaking space ( ) to separate the symbols. For example, ms is the symbol for the millisecond, while m·s or m s is the symbol for the metre-second.
• When unit symbols are combined by division, use a slash to separate the symbols (e.g., for the metre per second use the symbol m/s, not mps) or use negative exponents (m·s⁻¹). Exceptions include "mph" for the mile per hour, "psi" for pounds per square inch, etc.
  • There should be no more than one slash per compound unit symbol, e.g., kg/(m·s), not kg/m/s or kg/m·s.
• Powers of unit symbols are expressed with a superscript exponent (write 5 km², not 5 km^2).
  • A superscript exponent indicates that the unit is raised to a power, not the unit and the quantity (3 metres squared is 9 square metres, or 9 m²).
  • For areas and volumes, squared and cubed US customary or imperial length units may instead be rendered with "sq" and "cu" between the number and the unit symbol (e.g., 15 sq mi and 3 cu ft, not 15 mi sq and 3 ft cu).
  • The symbols "sq" and "cu" are not used with BIPM-approved unit symbols.
  • Avoid the Unicode characters "²" and "³". They are harder to read on small displays, and are not aligned with superscript characters (see "x¹x²x³x⁴" vs. "x¹x²x³x⁴"). Instead, use superscript markup, created with .
• Numerical range of values are formatted as lower value-en dash-higher value-non breaking space-unit symbol (e.g., 5.9–6.3 kg, not 5.9 kg – 6.3 kg or 5.9 – 6.3 kg), or can be specified in written form using either unit symbol or unit names, and units can be stated either after both numerical values or after the last (e.g., from 5.9 to 6.3 kilograms, from 5.9 kilograms to 6.3 kilograms, from 5.9 to 6.3 kg and from 5.9 kg to 6.3 kg are all acceptable, but only one of these format should be in use in a given article).
• When dimensions are given, values each number should be followed by a unit name or symbol (e.g., write 1 m × 3 m × 6 m, not 1 × 3 × 6 m or 1 × 3 × 6 m³).

Units and symbols often written incorrectly

• The degree symbol is °. Using any other symbol (e.g., masculine ordinal º or ring above ˚) for this purpose is incorrect.
• The symbol for the bit is bit, not b. The byte may be represented by either one of the symbols B and byte, but not b or o (French octet). Unless explicitly stated otherwise, one byte is eight bits (see History of byte).
  • By extension, the symbols for the units of data rate kilobit per second, megabit per second and so on are kbit/s (not kbps or Kbps), Mbit/s (not Mbps or mbps), etc. Similarly, kilobyte per second and megabyte per second are kB/s (not kBps or KBps) and MB/s (not Mbps or MBps).
• The symbols for Celsius degrees, Fahrenheit degrees and kelvins are °C (not C), °F (not F), and K (not °K).
• For reasons of legibility, the preferred symbol for the unprefixed liter is upper-case L.
• If you need to express years as a unit, use the symbol a (from the Latin annum) along with SI prefixes (e.g., write The half life of thorium-230 is 77 ka and The Cambrian is a geologic period that dates from 540 Ma to 490 Ma).
  • There are many types of years (see year). When years are not used in the layman's meaning (e.g., Julie is 20 years old) clarify which type of year is meant.
• Roman prefixes are not used (M (10³), MM (10⁶), B (10⁹)). Use SI prefixes instead.

Quantities of bytes and bits

In quantities of bits and bytes, the prefixes kilo (abbreviated k or K), mega (M), giga (G), etc. are ambiguous. They may be based on a decimal system (like the standard SI prefixes), meaning 10³, 10⁶, 10⁹, etc., or they may be based on a binary system, meaning 1024 (2¹⁰), 1024², 1024³, etc. The binary meanings are more commonly used in relation to solid-state memory (such as RAM), while the decimal meanings are more common for data transmission rates and disk storage.

Multiple-byte units
Decimal Value Metric 1000 kB kilobyte 10002 MB megabyte 10003 GB gigabyte 10004 TB terabyte 10005 PB petabyte 10006 EB exabyte 10007 ZB zettabyte 10008 YB yottabyte 10009 RB ronnabyte 100010 QB quettabyte	Binary Value IEC Memory 1024 KiB kibibyte KB kilobyte 10242 MiB mebibyte MB megabyte 10243 GiB gibibyte GB gigabyte 10244 TiB tebibyte TB terabyte 10245 PiB pebibyte — 10246 EiB exbibyte — 10247 ZiB zebibyte — 10248 YiB yobibyte — — —
Orders of magnitude of data

The following recommendations are made for the use of these prefixes in Wikipedia articles:

• Editors should specify if the binary or decimal meanings of K, M, G, etc. are intended as the primary meaning. Consistency within each article is desirable, but the need for consistency may be balanced with other considerations.
  • The definition most relevant to the article should be chosen as primary one for that article (e.g., specify a binary definition in an article on RAM, decimal definition in an article on hard drives, and a binary definition for Windows file sizes, despite files usually being stored on hard drives).
  • Where consistency is not possible, specify wherever there is a deviation from the primary definition.
• Disambiguation should be shown in bytes or bits, with clear indication of whether in binary or decimal base. There is no preference in the way to indicate the number of bytes and bits, but the notation style should be consistent within an article. Acceptable examples include:

A 64 MB (64 × 1024² bytes) video card and a 100 GB (100 × 1000³ bytes) hard drive

A 64 MB (64 × 2²⁰ bytes) video card and a 100 GB (100×10⁹ bytes) hard drive

A 64 MB (67,108,864 bytes) video card and a 100 GB (100,000,000,000 bytes) hard drive

Avoid inconsistent combinations such as A 64 MB (67,108,864 bytes) video card and a 100 GB (100 × 1000³ bytes) hard drive. Footnotes, such as those seen in Power Macintosh 5500, may be used for disambiguation.

The IEC standard prefixes kibi-, mebi-, gibi-, etc. (symbols Ki, Mi, Gi, etc.) are not familiar to most Wikipedia readers, so are generally not to be used except under the following circumstances:

• when the article is on a topic where the majority of cited sources use the IEC prefixes,
• when directly quoting a source that uses the IEC prefixes,
• in articles specifically about or explicitly discussing the IEC prefixes.

Currencies

See also: Wikipedia:WikiProject Numismatics/Style § Article titles

Which one to use

• In country-specific articles, such as Economy of Australia, use the currency of the country.
• In non-country-specific articles such as Wealth, use US dollars (US$123), the dominant reserve currency of the world. Some editors also like to provide euro and/or pound sterling equivalents, formatted as described in the next section.

Formatting

• Fully identify a currency on its first appearance (AU$52); subsequent occurrences are normally given without the country identification or currency article link (just $88), unless this would be unclear. The exception to this is in articles related entirely to US- or UK-related topics, in which the first occurrence may also be shortened and not linked ($34 and £22, respectively), unless this would be unclear. Avoid over-identifying currencies that cannot be ambiguous; e.g., do not place EU or a similar prefix before the € sign.
• Do not place a currency symbol after the value (123$, 123£, 123€), unless the symbol is normally written as such. Do not write $US123 or $123 (US).
• Currency abbreviations that come before the number are unspaced if they consist of or end in a symbol (£123, €123), and spaced if alphabetic (R 75).
• If there is no common English abbreviation or symbol, use the ISO 4217 standard.
• Ranges are preferably formatted with one rather than two currency signifiers ($250–300, not $250–$300).
• Conversions of less familiar currencies may be provided in terms of more familiar currencies, such as the US dollar, euro or pound sterling. Conversions should be in parentheses after the original currency, rounding to the nearest whole unit, with at least the year given as a rough point of conversion rate reference; e.g., 1,000 Swiss francs (US$763 in 2005).
• For obsolete currencies, provide if possible an equivalent, formatted as a conversion, in the modern replacement currency (e.g. decimal pounds for historical pre-decimal pounds-and-shillings figures), or at least a US-dollar equivalent as a default in cases where there is no modern equivalent.
• When possible, always link the first occurrence of a symbol for lesser-known currencies (₮146); some editors consider it unnecessary to link the symbols of well-known currencies, but doing so can often be helpful to readers, as many countries use "dollars" or "pounds" as their base currency, and not all readers are familiar with the euro.
• The names of currencies, currency subdivisions, coins and banknotes should not be capitalised except where normal capitalisation rules require this (for example, at the start of a sentence).
• The pound sterling is represented by the £ symbol, with one horizontal bar. The double-barred ₤ symbol is ambiguous, as it has been used for Italian lire and other currencies as well as that of the British. For non-British currencies that use pounds or a pound symbol (e.g. the Irish pound, IR£) use the symbol conventionally preferred for that currency.

Common mathematical symbols

See also: Manual of Style (mathematics).

• For a negative sign or subtraction operator, use a minus sign (−). You can input a minus sign by either keying in &minus; or by clicking on it in the insert box beneath the edit window (located between the ± and × signs). Do not use an en dash (–), do not use a hyphen (-) unless writing code, and do not use an em dash (—).
• For a multiplication sign, use ×, which is input by clicking on it in the edit toolbox under the edit window or by keying in &times; (however, the letter x is accepted as a substitute for "by" in such terms as "4x4").

Common mathematical symbols

Name	Operation	Other use	Symbol	Wikicode	ASCII	Unicode	As binary operator (e.g. 1 + 1)	As unary operator (e.g. +1)
Plus sign	Addition	Positive sign	+	+	+	U+002B	Spaced	Unspaced
Plus or minus	Addition or subtraction	Positive or negative sign	±	±	±	U+00B1	Spaced	Unspaced
Minus or plus	Subtraction or addition	Negative or positive sign	∓	—	∓	U+2213	Spaced	Unspaced
Minus sign	Subtraction	Negative sign	−	−	−	U+2212	Spaced	Unspaced
Multiplication sign, cross	Multiplication, vector product	—	×	×	×	U+00D7	Spaced	—
Division sign, obelus	Division	—	÷	÷	÷	U+00F7	Spaced	—
Equal sign	Equation	—	=	—	=	U+003D	Spaced	—
Not equal sign	Non-equation	—	≠	≠	≠	U+2260	Spaced	—
Approximate sign	Approximation	—	≈	≈	≈	U+2248	Spaced	—
Less than sign	Inequation	—	<	&lt;	&#60;	U+3C	Spaced	—
Less than or equal to	Inequation	—	≤	&le;	&#8804;	U+2264	Spaced	—
Greater than sign	Inequation	—	>	&gt;	&#62;	U+3E	Spaced	—
Greater than or equal to	Inequation	—	≥	&ge;	&#8805;	U+2265	Spaced	—

Unnecessary vagueness

Use accurate measurements whenever possible.

Vague	Precise
The wallaby is small	The average male wallaby is 1.6 metres (63 in) from head to tail.
Prochlorococcus marinus is a tiny cyanobacterium.	The cyanobacterium Prochlorococcus marinus is 0.5 to 0.8 micrometre across.
The large oil spill stretched a long way down the Alaskan coast.	The oil spill that drifted down the Alaskan coast was 3 statute miles (5 km) long and 1,000 feet (300 m) wide.
A beautiful little house in Malibu	A $400,000 residential property in Malibu

Geographical coordinates

For draft guidance on, and examples of, coordinates for linear features, see Wikipedia:WikiProject Geographical coordinates/Linear.

Quick guide:

Quick how-to

To add 57°18′22″N 4°27′32″W to the top of an article, use {{Coord}}, thus:

{{Coord|57|18|22|N|4|27|32|W|display=title}}

These coordinates are in degrees, minutes, and seconds of arc.

"title" means that the coordinates will be displayed next to the article's title at the top of the page (in desktop view only; title coordinates do not display in mobile view) and before any other text or images. It also records the coordinates as the primary location of the page's subject in Wikipedia's geosearch API.

To add 44.1124°N 87.9130°W / 44.1124; -87.9130 to the top of an article, use either

{{Coord|44.1124|N|87.9130|W|display=title}}

(which does not require minutes or seconds but does require the user to specify north/ south and east/west) or

{{Coord|44.1124|-87.9130|display=title}}

(in which the north and east are presumed by positive values while the south and west are negative ones). These coordinates are in decimal degrees.

• Degrees, minutes and seconds, when used, must each be separated by a pipe ("|").
• Map datum must be WGS84 if possible (except for off-Earth bodies).
• Avoid excessive precision (0.0001° is <11 m, 1″ is <31 m).
• Maintain consistency of decimal places or minutes/seconds between latitude and longitude.
• Latitude (N/S) must appear before longitude (E/W).

Optional coordinate parameters follow the longitude and are separated by an underscore ("_"):

• dim: dim:N (viewing diameter in metres)
• region: region:R (ISO 3166-1 alpha-2 or ISO 3166-2 code)
• type: type:T (landmark or city(30,000), for example)

Other optional parameters are separated by a pipe ("|"):

• display

  |display=inline (the default) to display in the body of the article only,

  |display=title to display at the top of the article only (in desktop view only; title coordinates do not display in mobile view), or

  |display=inline,title to display in both places.

• name

  name=X to label the place on maps (default is PAGENAME)

Thus: {{Coord|44.1172|-87.9135|dim:30_region:US-WI_type:event

|display=inline,title|name=accident site}}

Use |display=title (or |display=inline,title) once per article, for the subject of the article, where appropriate.

• Per WP:ORDER, the template is placed at the bottom of the article in the 'end matter', after any navigation templates, but before all categories, including the {{DEFAULTSORT}} template. The {{coord}} template may also be placed within an infobox, instead of at the bottom of the article.
• For full details, refer to {{Coord/doc}}.
• Additional guidance is available at obtaining coordinates and converting coordinates.

Geographical coordinates on Earth should be entered using a template to standardize the format and to provide a link to maps of the coordinates. As long as the templates are adhered to, a robot performs the functions automatically.

First, obtain the coordinates. Please don't be overly precise.

Two types of template are available:

• {{coord}}, which has replaced the coor family (and combined their functionality), offers users a choice of display format through user styles, emits a Geo microformat, and is supported by Google Earth.
• Infoboxes such as {{Infobox settlement}}

Depending on the form of the coordinates, the following formats are available.

For just degrees (including decimal values):

{{coord|dd|N/S|dd|E/W}}

For degrees/minutes:

{{coord|dd|mm|N/S|dd|mm|E/W}}

For degrees/minutes/seconds:

{{coord|dd|mm|ss|N/S|dd|mm|ss|E/W}}

where:

• DD, MM, SS are the degrees, minutes, seconds, listed in sequence
• N/S is either N or S, depending on which hemisphere, and
• E/W is either E or W, depending on which hemisphere
• negative values may be used in lieu of S and W

For example:

The city of Oslo, located at 59° 55′ N, 10° 44′ E, enter:

{{coord|59|55|N|10|44|E}} — which becomes 59°55′N 10°44′E

A country, like Botswana, less precision is appropriate:

{{coord|22|S|24|E}} — which becomes 22°S 24°E

Higher levels of precision are obtained by using seconds

{{coord|33|56|24|N|118|24|00|W}} — which becomes 33°56′24″N 118°24′00″W

Coordinates can be entered as decimal values

{{coord|33.94|S|118.40|W}} — which becomes 33.94°S 118.40°W / -33.94; -118.40

Increasing or decreasing the number of decimal places can control the precision. Trailing zeroes should be included.

London Heathrow Airport, Amsterdam, Jan Mayen and Mount Baker are examples of articles that contain geographical coordinates.

Generally, the larger the object being mapped, the less precise the coordinates should be. For example, if just giving the location of a city, precision greater than 100 meters is not needed unless specifying a particular point in the city, for example the central administrative building. Specific buildings or other objects of similar size would justify precisions down to 10 meters or even one meter in some cases (1′′ ~15 m to 30 m, 0.0001° ~5.6 m to 10 m).

The final field, following the E/W, is available for specification of attributes, such as type, region and scale.

When you have added the coordinates, you might want to remove the {{coord missing}} tag from the article, if present.

For more information, see the geographical coordinates WikiProject.

Templates other than {{coord}} should use the following variables for coordinates: lat_d, lat_m, lat_s, lat_NS, long_d, long_m, long_s, long_EW.

See also

• For page naming specifics, see Wikipedia:Naming conventions (numbers and dates).
• m:Help:Date formatting feature at Meta
• Displaying numbers and numeric expressions

Notes