Talk:Metric prefix

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Contents

Proposed Extensions[edit]

I altered the OP's post stating, "Of these only the litre is still in ubiquous(sic) use." In my experience, what the OP defines as an "are" is known as a(n) "hectare", that being an area equal to 56,000m2[1] (100mx100m). This term is used VERY widely as a pseudo-SI alternative to "acre" when talking about land and must, I would think, qualify as being in "ubiquitous" use? Also according to Google[2], an "are" is 1/100th of a hectare, or 10m2. As a result of this supporting evidence, I also altered the relevant parts of the post to reflect these values.64.201.173.205 17:49, 21 March 2006 (UTC)

I'm not quite sure of where your figure of 56000 m2 comes from. It doesn't seem to have influenced anything in the article, so there's no harm done. Obviously 100 m x 100 m is 10000 m2 = 1 hectare. Yes, an "are" is an area of 100 m2, and is used in Spain for measuring the floor space of buildings.--King Hildebrand 16:50, 2 August 2006 (UTC)

Dumphrey[edit]

The article claims that a liter is sometimes "referred to as a 'dumphrey'". I couldn't verify that claim and removed it. AxelBoldt

Binary prefixes[edit]

The powers of two have a new SI standard, IINM. 210 bytes == 1 Kibibyte (1 KiB), 220 bits == 1 Mebibit (1 Mib), 230 bytes = 1 Gibibyte (1 GiB). -- Hari (2002-03-18)

See http://physics.nist.gov/cuu/Units/binary.html, for instance -- Hari (2002-03-18)

Could you add an explanation to that effect? Such as "KiB should be used instead of KB...". (It's not a SI standard however.) AxelBoldt

Does anyone have an objction to me moving most of the explanation of byte prefixes to Byte prefixes, and leaving just a short paragraph on it here & a link? -- Tarquin 14:45 Jan 12, 2003 (UTC)
I've renamed it to "Binary prefixes". It's used for anything based on the power of 2 (e.g., bits, words), not just bytes. -- Dwheeler 20:12 21 May 2003 (UTC)

In my opinion, the whole "Computing" section must go. It is entirely incorrect when using the rules of the SI. The SI does not define any special exceptions to do with computing, and this entry implying such is incorrect. It's fine if we move this to a new entry, but it must be very clear that such usage goes against the SI. --Eliasen 11:07, 28 Nov 2004 (UTC)

I agree. Remove the section and direct them to binary prefix. - Omegatron 22:36, Mar 3, 2005 (UTC)

A vote has been started on whether Wikipedia should use these prefixes all the time, only in highly technical contexts, or never. - Omegatron 14:56, July 12, 2005 (UTC)


"iso" prefix[edit]

I've just added this. Gritchka I have to say I've never seen 'iso' mentioned in this context. What's the authority for this?

I've never heard of it. My encyclopedia doesn't give it in the table of SI. Official reference such as http://physics.nist.gov/Pubs/SP811/sec04.html doesn't give it. The only link I have found on google about it seems contentious (Star Trek science). It's also faintly ludicrous -- a metre is a metre. What is the point of saying "isometre"? Just to clinch it, the official site http://www.bipm.fr/enus/3_SI/si-prefixes.html makes no mention of it. I think someone thought "isobar" was a prefix applied to "bar", whereas it's a line of constant value on a map. In short, I can't find any evidence of its existence, rather, I'm finding evidence of its non-existence. It's going. It's gone ;-) -- Tarquin 00:34 Sep 15, 2002 (UTC)

Subdividing these?[edit]

It's all very well with the prefixes given here, but what about for example organic chemistry? You require extra endings for 2, 3, 4, 5, 6... (Okay, so they start meth- eth- prop- but-, but that's not the point... think about silanes.) What are the prefixes for 1, 2, 3, 4, 5...?


I don't understand your question. There are only prefixes for powers of 10. The prefixes used for systematic chemical names have nothing to do with SI -- Tarquin 23:04, 2 Oct 2003 (UTC)


No one ever answered the OP's question, and since it's almost been a decade... an appropriate "metric like multiple" of the year (or the 'ade'?)... Silanes sequence similarly to methane, ethane... by using

silane, disilane, trisilane, tetrasilane, pentasilane... at which point they use the same prefixes as the alkane series there once you reach penta. —Preceding unsigned comment added by 130.111.163.179 (talk) 15:48, 31 March 2010 (UTC)

"Billiard", etc[edit]

Do the number names "billard", "trilliard", etc, really exist? "Milliard" is old-fashioned (possibly archaic) in UK usage although its cognates are current in some European languages. I have never seen "billiard", etc, listed in any printed dictionary, except as "billiards", which is a game similar to pool. The UK, as has been pointed out on the page, now tends to use "billion", etc, in the same way as they are used in the UK. Other European languages vary between the US system and the older UK system. Could someone point out an authoratitive reference that lists these terms? If not, could I suggest they are removed or marked as neologisms, for the nonce, rare, jokey, or something else? Thanks. -- Paul G 09:57, 12 Jan 2004 (UTC)

At least in Swedish, the series Miljon, Miljard, Biljon, Biljard etc. series is used.
Mark these old-fashioned possibly archaic words as neologisms, 'ay? You can't have it both ways. Yes, they do exist though, alas, rarely used in English these days. My vote would be to leave them in. The reason: the original naming system of numbers (what Wikipedia calls the long scale) is logical and therefore easier to understand especially for speakers of other European languages. Jimp 13Oct05
You can indeed have it both ways. "Milliard" is unknown in US English and archaic in UK English. "Billiard", "Trilliard", etc. are simply not English words, despite being used in other European languages. Other than tables of names of numbers you will be hard pressed to find these terms in either modern or historical English sources. —Preceding unsigned comment added by 128.146.32.245 (talk) 20:27, 27 May 2010 (UTC)
As an American living in the Netherlands and working with Dutch and German co-workers, I run into the "billion/biljoen problem" somewhat regularly. Keeping the SI Prefix chart with both the "short scale" and the "long scale" is a very useful reference when crossing in and out of english while talking about big numbers. In "long scale" (what my co-workers natively think in) 1000000^1 is a million, 1000000^2 billion, 1000000^3 is a trillion, thus the prefixes match the exponents of 1000000. In short scale 1000^3 a billion, 1000^4 is a trillion, 1000^5 is a quadrillion, which strikes some of my non-american co-workers as strange because the prefixes don't seem to match the exponents. I would suggest the chart could be improved by adding a "1000000 to the X" column. That might really demonstrate the straight-forward logic of the "SI long scale" to us "short scale" readers and also show the "off by one" with the short scale (something I didn't understand until working with "long scale" thinkers for a little while). EricHerman (talk) 10:23, 1 October 2008 (UTC)

Nonna, Dogga, etc.[edit]

Is there any reason that Nonabyte and Doggabyte haven't been added to this list yet? I was going to add them myself, but I wanted to clarify that their British name would be "Thousand Quadrillion" and "Quintillion", and that their symbols would be 'N' and 'D'. Does anyone have any authoritative sources on these? -- DropDeadGorgias 17:16, 19 Feb 2004 (UTC)

Because they are not real SI prefixes? -- The Anome 06:00, 1 Apr 2004 (UTC)

To answer this question about Nona and Dogga, there have been various times in history when nonabyte existed as a Wikipedia article, but it always went onto the "votes for deletion" page. About 90% of all Wikipedians agree that it shouldn't have a Wikipedia article. 66.245.30.189 02:01, 1 Apr 2004 (UTC)

There is a place for Non-SI unit prefixes. Why not putthese there? Jimp 13Oct05

Prefixes for 10^27 and 10^30[edit]

The creator of the Names of large numbers article has a part that uses SI prefixes for part of it that goes past yotta for xenna and viki. 66.32.148.174 23:13, 3 Jun 2004 (UTC)

Prefix for 10^27??[edit]

I contacted the webmaster of bimp.org and they say that they will not confirm a prefix for 10^27 as of 2005. Any comments?? 66.245.95.15 16:29, 2 Jul 2004 (UTC)

Surely the entry for Bronto must be removed until such time as this is confirmed by SI / BIPM?
The BBC has just written an article mentioning Brontobyte [[3]] as 10^27, but, Googling, there seems to be few precedents - a Sybase article [[4]](which can't even spell yottabyte); a UCL article [[5]] which puts a Brontobyte at 1000 Eb = 10^21 = Zettabyte?? An American article [[6]] which thinks that Brontobyte = Petabyte = 10^15 - and none of these cite any de jure authority. Does anybody know the origin for this proposed term?? Given the ambiguity, surely it has to go? Ian Cairns 23:00, 20 Sep 2004 (UTC)

Petition going around for 10^27 to be designated 'hella' [[7]] —Preceding unsigned comment added by 76.65.198.191 (talk) 14:43, 7 July 2010 (UTC)

What is the proposed symbol for hella? —Preceding unsigned comment added by 24.252.146.105 (talk) 20:39, 7 July 2010 (UTC)


I stumbled upon the use of 'bronto-' and 'geop-' on a page about HP's Machine: http://www8.hp.com/hpnext/posts/discover-day-two-future-now-machine-hp#.U5ukLlQch0u. Pretty sure that's not enough to include them in the article but it's worth signaling.--Grondilu (talk) 01:28, 14 June 2014 (UTC)

Bilion[edit]

According to billion and Fowler, 'billion' can mean both 10^9 and 10^12 in the UK. Best to not mention it in the table headers -- Tarquin 08:57, 21 Sep 2004 (UTC)

The 10^12 meaning is utterly obsolete in the whole English-speaking world. As this is the English Wikipedia, the "long scale" column should really be removed to prevent needless confusion. – Smyth 13:02, 27 Sep 2004 (UTC)

Bogus SI prefixes[edit]

The category Category:Bogus SI prefixes contains a whole bunch of stubs that look to me like they're unlikely to grow. Anyone object if I merge them all into Bogus SI prefix or something similar? Bryan 05:33, 14 Oct 2004 (UTC)

Mega[edit]

How popular of a belief is it that it is okay to use mega- as a numerical prefix for a million (as if it belonged in the regular Greek numerical prefixes article)?? It is not in there; its literal meaning is "great". 66.32.255.51 01:29, 31 Oct 2004 (UTC)

Never heard someone use it. Chemicals pentane, hexane, ...., mega-ane? No way, you'd call the latter simply polyethene. I can't think of a situation right now where it could be used. A numerical prefix suggests that it is exact (1,000,000 and not 1,000,002) which usually doesn't make much sense for big numbers. Han-Kwang (talk) 12:08, 16 Nov 2004 (UTC)
Megaton is used for an explosion equivalent to 1 million tons of TNT. Is this an example of what you mea, or have I got hold of the wrong end of the stick?--King Hildebrand 15:41, 2 August 2006 (UTC)

What about a Megalith - just a big rock not a million of anything! (Chris Neale)

cc[edit]

Do doctors in American medical soap operas always say "cc" (short for "cubic centimetre") to mean "millilitre" because they don't want the audience to know they're using a metric unit? At least here in Finland, "millilitre" is a much more widely known unit than "cubic centimetre", even though they're the same thing. JIP | Talk 17:17, 1 May 2005 (UTC)

No, all doctors in America use cc. Cburnett 17:25, May 1, 2005 (UTC)
Why do they call it cc instead of millilitres, then? JIP | Talk 18:52, 1 May 2005 (UTC)
I wouldn't tak that as an established fact based on one person's comments. For example, what specific context do you have in mind? Liquid drugs are usually labeled in milliliters, and so prescribed. What's used for capacity of syringes? For cranial capacity? The more prevalant usage can be different in different contexts.
You are probably just a kid who doesn't remember the days when we had to learn that milliliters and cubic centimeters are different units. Some of the usage habits today go back to those days when a distinction was sometimes made for clarity, even though very few measurements were ever precise enough to tell he difference. That's just one of the factors that come into play--but fooling the audience into thinking they are not using a metric units is one of the least plausible factors. Your theory doesn't hold any water. Americans know that it is a metric unit, whether it is "cc" or "cm³" or "mL". Gene Nygaard 19:23, 1 May 2005 (UTC)
Actually, I've even seen liquid drugs measured in miligrams. In particular, morphine. Measuring liquids in cc's and solids in mg's are probably the most prevalent. I've *never* had a prescription filled in grains or ounces. :) But whatever is used and why, it has little to do with "fooling the audience". Cburnett 22:46, May 1, 2005 (UTC)
Really? I'm sure it was expressed in milligrams per mL if you check again. —Preceding unsigned comment added by 96.36.25.88 (talk) 04:15, 16 May 2009 (UTC)
If close to 30 years is "just a kid" to you, then I agree. But no, I don't remember ever learning that cubic centimetres and millilitres are any different. JIP | Talk 04:27, 2 May 2005 (UTC)
From 1901 until 1964, 1 ml was approximately 1.000028 cm³. The liter was then defined as the volume of one kilogram of water at its maximum density, rather than as a cubic decimeter.Gene Nygaard 04:40, 2 May 2005 (UTC)
Figures, seeing as I wasn't born in 1964. My parents hadn't even met each other then. The bit about fooling the audience was pure speculation on my part. JIP | Talk 14:48, 3 May 2005 (UTC)

An old man such as myself remembers that many of our American textbooks of the late 1940 to pre-1970 era distinguished them as: cc = volume, ml = capacity (the latter being contingent on positive, neutral or negative meniscus formation of liquids). I hope this is some help; Dr.R.E.Petrere

Non-standard prefix abbreviations?[edit]

What about non-standard abbreviations, such as "mc" or "u" for "micro"? --Carnildo 17:41, 20 Jun 2005 (UTC)

That's talked about at micro. Lee S. Svoboda 20:25, 7 October 2005 (UTC)
From micro: "In circumstances where only the Latin alphabet is available, the SI standard allows representation of the prefix using the letter u as in um for µm, or uV for µV." This assertion must be sourced or deleted. I didn't find this statement of this in SI Brochure (http://www.bipm.org/en/si/si_brochure/) so I think this use is not allowed officially. Please provide a source or it will be deleted. Armando82 11:04, 20 April 2007 (UTC)
I strongly feel it should be mentioned/noted that 'u' is used in some contexts as a replacement abbreviation for micro. Though it is not in the standard, it's widely used in reference to microfarads, especially on electronics hobbyist websites: [8] [9] [10] [11] and the writers assume that the reader will understand that 'u' means 'micro' in this context. It should definitely be noted, though, that this is not standard. (The same websites tend not to put spaces between the number and the unit, too--also nonstandard.) The belief that the 'u' abbreviation is standard may stem from the belief that the (withdrawn/retracted) ISO 2955 linked at the bottom of the article is part of the SI, which it isn't. 12.218.76.10 (talk) 16:03, 1 July 2014 (UTC)

Merge with SI#SI prefixes[edit]

Shouldn't this be merged with SI#SI prefixes? They seem to have very similar contents.

Lee S. Svoboda 20:28, 7 October 2005 (UTC)

Yes, SI#SI prefixes should be moved here. The article SI is far too large as it is. Moving the bulk of SI#SI prefixes here would help make SI a more manageable size. Jimp 13Oct05
It's done. Jimp 14Oct05

History of the SI prefixes?[edit]

Does anyone have solid information on when the various SI prefixes were first introduced? I am under the impression that prefixes through mega/micro go back to the beginning of the Metric system, tera, giga, nano and pico go back to the intro of SI in 1960 (though they must have been discussed earlier) and the rest are newer (1980s??) . But it would be interesting to pin down dates and maybe add them to the table in the article. --agr 21:46, 18 December 2005 (UTC)

I'd love to know this, too. "Many SI prefixes predate the introduction of the SI in 1960." How far? — Omegatron 15:00, 24 February 2006 (UTC)

Kilo[edit]

This term for 10^3 (1000) has existed since Greek has diverged from other Indo-European languages. The way Greek words normally come into English would have it be chilia, and the reason for the kilo spelling is unknown; I think it is disputed whether it is because ch can be pronounced differently by different languages, or whether they had centi- and didn't want the letter c to be ambiguous. Jimp 14Oct05

Well, according to http://www.chass.utoronto.ca/epc/langueXIX/nodier/ec_k.htm this is an "innovation". Which means, they started from the greek but simplified the word thru usage of what the author (a person from the XIXth century) a "new orthograph" : replacement of "ch" by a "k". So, as a summary this is an innovative word for an new way of mesuring the amounts, the SI .

BJB 13Jan2010 —Preceding unsigned comment added by 80.14.99.100 (talk) 15:49, 13 January 2010 (UTC)

Some transcriptionists always used kh for the greek letter chi. So, that khilia gave rise to kilo is a rational explanation. The French digraph ch is an English sh, we'd have "shillo-meters". French c before i sounds as English s, we'd have "sillo-meters". Logically, the best way to keep a hard aspirated k sound is to use the letter k. It wasn't thus so 130.111.163.179 (talk) 15:55, 31 March 2010 (UTC)innovative.

Mega[edit]

This term, I think, was coined in 1874 by someone who thought an SI prefix was needed for 10^6. They knew Greek didn't have a word for a million, so they just decided to coin a term coming from a word meaning "great".

Giga and Tera[edit]

These terms were coined by extrapolating mega for great by including giga- for giant and tera- for monster, both from Greek.

Peta and Exa (the ones I think are absurd)[edit]

These terms are the ones I think are absurd because of how they originated. Do you hear stories like these??

Let's make up 3 characters named George Washinton, Thomas Jeffeson, and Benjamin Franlin. We made up these characters' names by taking names of famous people and dropping one letter out.

Then, a forger who stumbles across the story with the names falsifies the names by adding in the letter dropped out.

The people who coined these prefixes in 1975 must not have been thinking of these, but because this is how these prefixes came into existence, I regard them to be absurd!

This looks like a fascinating explanation, but I suspect it needs a bit of clarification. I, personally, can't see any link at all between the story and the prefixes. Sorry to be dim, and all that! Could someone (possible the original anonymous poster) please explain a little more fully? Many thanks. --King Hildebrand 13:53, 2 August 2006 (UTC)
Sorry - I think Georgia Guy's signature applies to the whole section. I'll go and ask him... --King Hildebrand 13:54, 2 August 2006 (UTC)

Zetta and Yotta[edit]

These were the start of a sequence in descending alphabetical order all SI prefixes from this onward are expected to follow. Georgia guy 00:13, 1 May 2006 (UTC)

And one other thing to say[edit]

  • The next preifx, starting with X, whether xona- or xena-, how should the X be pronounced?? Georgia guy 00:34, 1 May 2006 (UTC)


Here's a page that contains the dates of adoption of every prefix:

http://web8.ehost-services.com/cdkaese/metre/prefixes.htm

Kilo [k] 103, one thousand; (from the Greek word khilioi, meaning thousand). This prefix was one of the original six prefixes of the metric system, when it became official on 1 August 1793.
Mega [M] 106, one million; (from the Greek word megas, meaning large). This prefix was introduced by the BA (British Association for the Advancement of Science) as part of the CGS-system of units in 1874 when the new units for electricity and magnetism were standardized.

etc. Very good information that we should include in this article. — Omegatron 22:53, 9 June 2007 (UTC)

Myriad[edit]

Myriad

You should include the myriad prefix (abbr. is unknown to me)even if it is disambuigated. You should also note that the term now means "a lot," "many," and/or/any combonation of/with "much." I cant find much info. on it but maybe you/othres can.


This is already noted as myria- and/or myio-......

I have also found myria- as prefix for meter (in Hungarian: miriaméter) in a Hungarian law from 1874, which implemented the SI in Hungary. Since this law implemented international standard, myria must have been an official SI standard then.Timur lenk 00:43, 24 September 2006 (UTC)

I think you are confusing the metric system with the International System of Units, which is symbolized "SI" in every language. SI was developed in 1960, and one of the goals was to discard obsolete, redundant, and ill-considered units. Myria- was discarded at that time. It's metric, but it's not SI. --Gerry Ashton 04:30, 25 February 2007 (UTC)

I dont know (Jiwe-)[edit]

Is it true that they used to have a unit called Jiwe-, I dont think so but it could be true. I think it was meant to be 1x10^3+.21/K (of same base unit)-13% of one uL. Quite complicated, huh.... I can see why they dropped it if it was evre used....

non-SI scales[edit]

"The reason various fields have develop their own non-SI scales is because of the problems posed by calculating very large or very small numbers on a computer accurately and efficiently. 1 angstrom is a lot easier for a computer to use in calculations than 1 × 10-10meter as truncation errors and rounding errors can occur losing accuracy in the calculation."

Speaking as a programmer, this is nonsense. Computers are very good at this sort of thing, and would work in floating point which would have no such limitations in the ranges spoken of. Also, the use of scaled units predates the wide use of computers, and may well be more historical than anything else. They may be inconvenient for people to work with, but that's a separate thing. I will remove this section. Notinasnaid 10:03, 1 June 2006 (UTC)

Giga pronounciation[edit]

[ˈgɪgə] and [ˈdʒɪgə]. The former is more common than the latter. How do you know this?Seforadev 03:55, 20 June 2006 (UTC)

Personal experience lends credence to the opinion in the article. I have been moving in scientific circles for forty or more years, and have very rarely heard the soft form, [ˈdʒɪgə], used. --King Hildebrand 13:44, 2 August 2006 (UTC)
I'm not a scientist, but I say 'gigabyte' with a hard G, and I have only ever heard it that way. The only time I've ever heard the soft one is in "1.21 gigawatts." 12.218.76.10 (talk) 15:00, 1 July 2014 (UTC)

Micron[edit]

The term "micron" is, I believe, non-standard. The SI prefers "micrometre". Thus "millimicron", given as an unapproved usage of combined prefixes is not a good example. After all, if you remove the prefixes you are left with nothing but the letter N! Micron, along with thou (one thousandth of an inch) are used familiarly by engineers, and are not part of SI. --King Hildebrand 13:39, 2 August 2006 (UTC)

Abbreviations D and H[edit]

When I was a kid, and first learned of these prefixes and abbreviations, I was taught that the correct abbreviations were D for deka, to distinguish it from deci, and H for hecto. The exception, I was taught, from capitals indicating positive powers, was k for kilo. The SI came into existence (1960) around the same time as I learned this, so my teacher (my mother) was probably not influenced by the authorities in Paris. In fact, I don't think I ever encountered da for deka before reading this article! Deka is probably the least used prefix.--King Hildebrand 16:40, 2 August 2006 (UTC)

deka[edit]

What is the correct form for deka? I think "k" is better than c, since the word derives from greek. Besides da, dk is also a common abreviation of deka (at least in the case of dekagram - dkg).Timur lenk 00:50, 24 September 2006 (UTC)

If you look at the the article's first external link, The International Bureau of Weights and Measures (BIPM): SI prefixes, you will see deca and da recommended. If you look at the third external link, US NIST "Definitions of the SI units: The twenty SI prefixes" you will see deka recommended, but the symbol recommendation is the same, da. So either is acceptable, but deka is preferred in the USA and deca is preferred elsewhere.
I live in the USA, and I don't recall ever seeing the deka prefix used, no matter how it is spelled. --Gerry Ashton 04:45, 24 September 2006 (UTC)
Thanks for the info. I live in Hungary and deka is commonly used in dekagram to measure mass in retail (typically sausage, cheese or such in a mall or grocery). The most widespread abbreviation is dkg, but very rarely dag can be seen as well. The form dkg is thaught in schools, too. Despite the practice in some other countries, grams are never used to measure mass (weight) in shops/groceries (you never ask for 300 g but for 30 dkg of cheese).
In an interwar Hungarian schoolbook (from the 1930s) I have seen deka as prefix of meter (forming dekameter), but it is totally unknown nowadays. Since the metric system was implemented by law in the 1870s, it can be an archaism - like myriameter (10 000 meter), which I have seen only in the above law.Timur lenk 10:10, 25 September 2006 (UTC)

Kilo, why k and not K?[edit]

Just a question if anyone knows. Why does kilo use (small) k and not (big) K as the other larger than 0 units? It's the same with deca (da) and hecto (h) but they are a bit outside since they don't follow the tree step thingie, so I can accept them. But I feel kilo should be K. So, why isn't it?

I ask this question because MSWord wants it to be K but safe sources say k. —The preceding unsigned comment was added by Thavox (talkcontribs) 11:49, 6 March 2007 (UTC).

The way I was taught is that when abbreviating units a letter is captialized only when the unit is named for a person or some other proper noun. For example the unit of force Newton is named after Isaac Newton so it is capitalized as "N" while the unit of length meter that is not named for anyone or any specific thing is a lower case "m". So the torque unit Newton-meter as I have seen it is usually abbreviated as "N-m". Other examples of capitalized units are Farad "F", Celsius "C", Joule "J" and Fahrenheit also "F". All named after real people that made significant contributions to physics. Heat units other than the Joule are British Themal Unit that is commonly capitalized as "Btu" (sometimes BTU) and calories that are abbreviated lower case as "cal" follow this convention. These days it seems that many of the computer related units do not follow the old convention. The prefixes giga and mega as related to computer science are usually abbreviated as "G" and "M" respectively. Also I don't think there ever was a "Mr. Byte" that made any significant contribution to computer science but hard drive capacities are routinely measured in "GB" and "TB" instead of "gb" and "tb". I'm sure there are many other exceptions. Having learned things this way I have always looked upon capitalizing certain units as a way of honoring truely exceptional people that changed every one of our lives for the better. At this point in my life I can say that there probably will never be a unit named after me but I can say with absolute certainty that you will never see me abbreviate a Newton as a simple lower case n. —Preceding unsigned comment added by 66.245.209.164 (talk) 05:16, 13 April 2008 (UTC)

The unit should be spelt newton, likewise it's kelvin, joule, farad, etc. degrees Celsius retains its capitalisation though. Degrees Fahrenheit is non-metric so the rule doesn't apply. The unit symbols are capitalised when named for a person and unit symbols not named for a person are generally not, however, there can be exceptions, the litre symbol, for example can be written as capital or lower case. The byte doesn't count since it's not a metric unit. However, that's the plain units we're talking about. The prefixes are a different story. Prefixes for a million and above are capitalised and those for less than a million are not. Why have the cut-off point somewhere between a thousand (or, more specifically, a myriad) and a million? That down to history, I s'pose they might have originally thought that 10,000 was large enough and 0.0001 small enough and decided to make all the prefix symbols lower-case, didn't think to revise it when they got to mega- and it ended up sticking. JIMp talk·cont 05:37, 5 June 2008 (UTC)

Excessive use of symbols[edit]

User: AnyFile recently revised the lead paragraph to avoid using spelled-out units and prefixes when preceded by a number. AnyFile stated that such usage was "not allowed by SI rules." I have seen style guides that encourage the use of symbols in scientific writing, but I am not aware of the prohibition mentioned by AnyFile in any publication that has the force of law. Furthermore, I believe spelling out the units is appropriate in a paragraph that is introducing readers to the concept of SI prefixes, advice in any style guide notwithstanding. --Gerry Ashton 14:03, 4 April 2007 (UTC)

Merge all the prefix articles[edit]

Should we merge all the articles like mega and giga into this article? They don't contain very much unique information . Most of it is redundant, and we already cover it all in here. They should be redirects with anchor tags going directly to the prefixes' definitions. — Omegatron 22:55, 9 June 2007 (UTC)

Oh. Gerry has a good point. Metric and SI are not the same, but share the same prefixes... — Omegatron 22:56, 9 June 2007 (UTC)

Small section commented out[edit]

"However, even some official prefixes may not be understood by all readers, let alone extrapolations of them, so giving an explanation is advisable when using them in communication (as opposed to using them in notes for oneself)."

This does not seem encyclopaedic. Comments? Rich Farmbrough, 11:00 13 June 2007 (GMT). 11:00, 13 June 2007 (UTC)


Mancho/mincho[edit]

I could not find any reference to the supposed prefixes "mancho" (1027) and "mincho" (10-27), so I removed them from the template. — Svenlafe 07:33, 20 June 2007 (UTC)

Requested move2[edit]

From Talk:Peta (prefix)#Requested move2:

Peta (prefix)peta- All prefixes should be moved to prefix- titles, as this is the standard way prefixes themselves are talked about and listed in dictionaries, and so that the (prefix) disambig isn't needed. — Omegatron 02:19, 23 June 2007 (UTC)

Digit grouping[edit]

User:Carlos Porto recently changed some, but not all, of the numbers in the article from using spaces between groups of three digits to using commas to group digits. There are arguments for and against this change:

For comma
The correct kind of space to use would be a non-breaking thin space. I don't know if such a space exists in Unicode, and if it does, I don't know how to enter it into the article. I also don't know how other editors would be able to tell that kind of space had been used.
For space
In those countries where a comma is usually used as a digit separator, it is usually only used to the left of the decimal point, but this article desperately needs a digit separator to the right as well. Since we have to use it to the right, we might just as well use it for everything.

In any case, I don't think it is correct to use a space to the left of the decimal for some numbers, but not for all. Comments? --Gerry Ashton 16:58, 7 July 2007 (UTC)

The argument for commas to the left is the MoS says

Commas are used to break the sequence every three places left of the decimal point; spaces or dots are never used in this role (2,900,000, not 2 900 000).

I'd prefer thin spaces both sides (it's doable, see Template:Delimitnum) but this discussion belongs elsewhere. JIMp talk·cont 05:53, 5 June 2008 (UTC)

Prefix choice[edit]

I don't have any suggestions, but I would have liked to see which is the "correct" way of reporting a length, for example: 450mm, 45cm, 4.5dm, or 0.45m? Is it a matter of taste? Dcaveney 15:44, 31 July 2007 (UTC)

For one thing, put a space between the numbers and the symbol. I don't have a source, but the trend is to only use prefixs where the multiplication or division is by a whole power of 1000. That is, kilo-, mega-, giga- or micro-, nano-, and pico-. Centi-, deka-, deci-, deka, and hecto- are used less and less. The exceptions that I'm aware of are centimeter and decibel.
The situation I could imagine using one of the more unusual prefixes in would be the face of a dial, where using one of these prefixes avoids the use of zeros or decimal points in marking the dial. --Gerry Ashton 18:53, 31 July 2007 (UTC)

The article says: "Prefixes corresponding to an exponent that is divisible by three are often recommended. Hence "100 m" rather than "1 hm" (hectometre) or "10 dam" (decametres). The "non-three" prefixes (hecto-, deca-, deci-, and centi-) are however more commonly used for everyday purposes than in science." Like Dcaveney and the author of the second paragraph in this section, I'd appreciate a reference for the divisible by three factoid. I think it's correct but I don't know its source. I don't think hecto- deca- or deci- are commonly used, here in the UK at least. I believe thay are used in some continental European countries. The centimetre is commonly used in the UK, probably because of the history of the cgs system. The decibel and hectare are also used, though neither would be completely familiar to the man in the street. 91.84.70.134 (talk) 23:19, 15 August 2010 (UTC)

I have a question[edit]

In the article I found the following to be unclear:

Prohibition of multiple prefixes The kilogram is the only SI base unit that has an SI prefix as part of its unit name and symbol. Because multiple prefixes may not be used (such as microkilogram or µkg), the prefixes are used with the unit gram and its symbol g (e.g. milligram or mg).

Could someone please explain the first sentence to me? The rest I follow. If I'm having problems with it, I know someone else must be having problems also. Bad S Mini (talk) 09:24, 29 November 2007 (UTC)Bad S Mini

The sentence just means that the name of the base unit of mass is kilogram and not gram. That makes it different from (say) kilometre, because the base unit of distance is metre. Thunderbird2 (talk) 09:41, 29 November 2007 (UTC)
I have just reworded this. Open4D (talk) 13:21, 20 December 2008 (UTC)

What's Missing?[edit]

10^±0, 10^±1, 10^±2, 10^±3, 10^±6, 10^±9... Where are the SI prefixes for 10^±4, 10^±5, 10^±7, 10^±8, etc? Novjunulo (talk) 23:32, 20 January 2008 (UTC)

No such prefixes exist. Instead, the decimal point should be moved and one of the standard prefixes should be used. For example, if someone wrote 1.403 × 104 m and you wished to use an SI prefix, you would rewrite it as 14.03 km. --Gerry Ashton (talk) 23:40, 20 January 2008 (UTC)
There are obsolete metric prefixes for 10±4. JIMp talk·cont 05:42, 5 June 2008 (UTC)

larger prefixes[edit]

Different sources mention larger prefixes than yotta and smaller ones than yocto, such as [12] where they are called "bogus" prefixes. For example tredo = 10-30. Is there an adoption process for those to become official SI prefixes? I believe to remember that "yotta" was also called a bogus prefix prior to 1991 when it was adopted as an official SI prefix.--Ratzer (talk) 12:06, 6 April 2008 (UTC)

Yes, changes to SI must be approved by the General Conference on Weights and Measures. --Gerry Ashton (talk) 15:18, 6 April 2008 (UTC)
Thank you for the general answer, but I meant it more specific: is there something in the pipeline to adopt more prefixes? When is the next meeting, and is this on the agenda?--Ratzer (talk) 11:01, 7 April 2008 (UTC)

xera[edit]

Is xera becoming a pseudostandard for the 1027 prefix?

This mainstream media article mentions xeraflop as a unit of computer performance.

Supercomputer sets record

The Wikipedia article for FLOPS also mentions xeraflop.

Is there a corresponding "small" 10-27 prefix?

What's beyond xera? If the trend continues, I'm guessing the prefix for 1030 will start with W.

--Kreline (talk) 02:59, 9 June 2008 (UTC)

No. All of the 'references' you'll find to the Xera prefix are about the Roadrunner FLOPS record. If you read a few of them you'll notice they're all using the exact same text so there is only a single article that ever used that prefix and it was then regurgitated all over the Web. So where did that article get the prefix? Why, Wikipedia of course! The Roadrunner record coincided with XeraFLOP being incorrectly listed as an SI prefix in the infobox on the FLOPS page. Clearly the original author referenced WP without any fact-checking and of course nobody else copy-pasting the text into their own website/blog/whatever bothered to check either. It's a textbook example of how Wikipedia can spread false information very quickly when people consider it authoritative and nobody checks references. -- ExNihilo (talk) 12:42, 19 June 2008 (UTC)
It has become the default reference and has more Google references than even the Yottaflop, so while it might not be the Queen's English reference, it's most definitely the common parlance. Lordvolton (talk) 23:08, 19 June 2008 (UTC)
Let's not bring your insanity in here aswell. We've been through this (multiple times) on the FLOPS Talk Page. Nothing you're saying makes any sense at all. -- ExNihilo (talk) 00:14, 20 June 2008 (UTC)

What about xona, weka, vunda, uda, treda, sorta, rinta, quexa, pepta, ocha, nena, minga and luma?[edit]

This is only one person's idea [13], but surely the scientific community are discussing pay comes after yotta? (although presumably it hasn't yet become SI). Is it worth starting a section on future units (how and when they will be discussed/selected?) Natebailey (talk) 13:06, 22 July 2008 (UTC)

Oops, I see it already exists - http://en.wikipedia.org/wiki/SI_prefix#Extension :-) Natebailey (talk) 13:09, 22 July 2008 (UTC)
Not anymore, it's been replaced with the joke "hella-" as a possible extension, which is a joke to include this. I think if anything the two should be swapped. Minimally both should be included. 216.21.233.2 (talk) 18:44, 9 February 2012 (UTC)

exo-[edit]

Why does Exo- redirect here? Because of its resemblance to exa-? It has an entirely unrelated meaning of its own. —Tamfang (talk) 19:09, 15 February 2009 (UTC)

Other and obsolete prefixes[edit]

The cited work by Brewster does mention myria-, but I see no definition for myrio-, nor do I see any mention of symbols for either. --Jc3s5h (talk) 19:08, 16 January 2010 (UTC)

Nike used http://histoire.du.metre.free.fr/fr/Pages/Sommaire/06.htm to support the claim that the prefixes double- and demi- were part of the original metric system. I would like to know more about what kind of source this is. --Jc3s5h (talk) 04:10, 17 January 2010 (UTC)

The source is the French law of 1795 which established the metric system, which I found on The History of the Meter. --Nike (talk) 05:28, 17 January 2010 (UTC)
Do you know if histoire.du.metre.free.fr is a personal web site, run by a well-known organization, or run by the government? --Jc3s5h (talk) 05:57, 17 January 2010 (UTC)
I found the site listed as a reference on the French Wikipedia. The translated version is a reference under meter. I don't know the owner. The text is an historical document of the French government, which may be found numerous places. Feel free to replace it with a different link. --Nike (talk) 06:27, 17 January 2010 (UTC)

Hella[edit]

There has been a bit of a revert war in regards to the "hella" petition. I was of the opinion that it was a bit silly and non-notable, but it seems to have received some attention in the media, including the BBC, so perhaps it should remain in the article. --Nike (talk) 00:17, 11 March 2010 (UTC)

I disagree with including it in the article. The hella petition is not being seriously considered by the BIPM, nor for that matter by any notable scientists, and until it does, it seems a non-notable and trivial topic even if there has been media coverage on it. Not that this is in any way relevant, but given that the student is from the United States, I would have thought his efforts would be more productive in furthering metrication than in creating a new SI prefix. Wcp07 (talk) 06:59, 11 March 2010 (UTC)
I've modified the part about Google "officially implementing" it, to simply "implemented". Google != International Committee for Weights and Measures, and as such, they can't "officially" do anything about it. They do own their own calculator, so they're free to do with that what they wish. It does appear that the student has contacted someone on the committee about this, and that a motion will be introduced. Still, I think most people will agree that the chances of it passing are "hella small". WTF? (talk) 20:32, 7 July 2010 (UTC)
I added in that Google's inclusion is that of an easter egg, not a serious inclusion. As well as reinstated Jim Blower's far more serious and likely proposal. 216.21.233.2 (talk) 19:01, 9 February 2012 (UTC)

Is "hella-" the most/only currently notable proposed extension?[edit]

I very much doubt it, but it's the only one mentioned. It's hard to figure out where one would even look for information about proposals for extensions of the system that are under serious consideration. I was trying to remember the prefixes that Greg Egan used in Schild's Ladder, and I was sure this article would at least have a pointer to something helpful—but it doesn't. (I finally remembered that one of them was "vendeka-".) False vacuum (talk) 16:14, 13 August 2010 (UTC)

I found this. http://www.cs.uwaterloo.ca/~alopez-o/math-faq/node54.html It claims nea as 10^27 dea as 10^30 and una as 10^33. It follows the pattern of Greek numbers representing 1000^X where X is the number. We will see what is chosen. I doubt hella will be chosen however.Donhoraldo (talk) 23:49, 28 October 2010 (UTC)
Not at all. This dates back to 2003: http://jimvb.home.mindspring.com/unitsystem.htm 216.21.233.2 (talk) 19:02, 9 February 2012 (UTC)

The footnote of the table[edit]

The footnote to the table says "The metric system was introduced in 1795 with six prefixes." This is not correct. There were eight, myrio- and myria-. They did get dropped in the 60s, but when the metric system was invented, there were still more than the six we retain from that event.

128.111.130.159 (talk) 01:14, 11 December 2010 (UTC)

NPOV statement re kilobits (kb)/kilobytes (KB)[edit]

'In non-standard use, K is often used as a symbol prefix to the units bit and byte to designate the binary prefix kibi = 210 = 1024. Again, try to set an example of encouraging standard usage ('k' for kilo, rather than 'K') in your field or business.'

This, especially the second sentence, clearly fails the NPOV test. In the IT industry a lowercase k means 1000 whereas a capital K means 1024: an important distinction that shouldn't be discouraged (as the above stement clearly does). 195.200.159.2 (talk) 10:38, 13 June 2011 (UTC)

Nem ertem: koczkaknak vagy szamítogepszakiknak: 0.111.222.568.652.365 — Preceding unsigned comment added by 188.6.105.34 (talk) 15:50, 23 January 2012 (UTC)

Move[edit]

These prefixes are metric prefixes. Many predate the SI. They are used for non-SI metric units (e.g. "millilitre", "hectare" & "kilocalorie") with the same meaning. Look at the following sentence. "The base unit of length in the cgs system is the centimetre." Is the "centi-" in that sentence an SI prefix? The SI is a metric system; it uses metric prefixes. There are other metric systems; they use the same prefixes. I propose we move the article to Metric prefix. JIMp talk·cont 00:45, 14 February 2012 (UTC)

Moved. JIMp talk·cont 08:04, 5 March 2012 (UTC)
They're defined in SI, even if they're used with other systems - which alone makes them SI prefixes. For that matter, they're used even outside metric, which by the logic above would just make them "unit prefixes". Furthermore, "SI prefix" is by far the most common term for them. I strongly suggest it's moved back to the original name. Kolbasz (talk) 22:52, 21 March 2013 (UTC)

Similar symbols in abbreviations[edit]

I dispute the assertion that "In other financial and business contexts, the letter M is often used to denote multiplication by 1000". A web search will show that the financial and general news media overwhelmingly use m/M, b/B and t/T as abbreviations for million, US billion and US trillion for large quantities, typically currency, population and geological time. Not withstanding the WP deprecation of primary research, my count of 1200 news headlines shows: thousand k = 52% (K = 48%); million m =77% (M = 23%); billion B = 58% (b = 42%); trillion T = 88% (t = 12%). The usage of 'm' is sanctioned in The Australian Government Style Guide (AGPS 2006, p.174), which recommends: "Millions of dollars may be expressed by placing 'm' (unspaced and without a full-stop) after the number (e.g. $2.751m)".

I agree that 'M' and 'MM' are used in U.S. oil industry publications, for oilfield reserves in barrels.

It's neat that the abbreviations M and T for million and trillion match the SI prefix symbols for mega and tera; it'd be even neater if the US oil industry stopped using 2000 year-old Roman numerals, and adopted the 200 year-old metric prefixes, but that's a POV, and not for publication on a WP article.

Adamtester (talk) 04:50, 14 February 2012 (UTC)

Why Yotta is Y and why Yocto is y ?[edit]

This is because the prefix Yotta is a much larger unit than Yocto and the letter Y is bigger than the letter y generated on the computer.

Copyright--207.237.10.60 (talk) 19:15, 23 February 2012 (UTC)

Binary prefixes and proposals[edit]

Metric prefixes are decimal. Binary prefixes may have the same names (unless you adhere to the IEC) but they're not metric. Binary prefixes have their own article. They don't need a whole section here.

Likewise the proposed prefixes are not metric in that they've not been adopted into the metric system. JIMp talk·cont 17:29, 2 March 2012 (UTC)

Merged to Unit prefix JIMp talk·cont 08:05, 5 March 2012 (UTC)

Binary prefix[edit]

Does the "binary prefix" mentioned in "Former metric prefixes" mean the same as what the article "binary prefix" talks about? If they are the same, we should make it a wiki link. --Quest for Truth (talk) 04:59, 6 May 2012 (UTC)

It is pushing a point to equate the two. The former metric prefixes were "half" and "double" whereas the binary prefixes are at least 1024. The prefix "half" is still in colloquial use - when in France, I will ask for a "demi-litre carafe vin du maison" (half a litre caraffe of the house wine). Martinvl (talk) 07:00, 6 May 2012 (UTC)

Angstrom[edit]

Why is this unit not included? 10^-10

Angstrom is not a prefix, it's a unit. Jc3s5h (talk) 15:26, 8 May 2012 (UTC)

Move to SI prefix[edit]

The following discussion is an archived discussion of a requested move. Please do not modify it. Subsequent comments should be made in a new section on the talk page. Editors desiring to contest the closing decision should consider a move review. No further edits should be made to this section.

The result of the move request was: Not moved. Apteva (talk) 15:59, 28 March 2013 (UTC)


Metric prefixSI prefix – The prefixes discussed in this article are defined in SI and are decided upon by CGPM resolutions, and are therefore SI prefixes. That some of the prefixes existed before SI or see use outside SI has no bearing. Kolbasz (talk) 23:26, 21 March 2013 (UTC)

Survey about move[edit]

Feel free to state your position on the renaming proposal by beginning a new line in this section with *'''Support''' or *'''Oppose''', then sign your comment with ~~~~. Since polling is not a substitute for discussion, please explain your reasons, taking into account Wikipedia's policy on article titles.
  • Support: As per my reason in the template, and my comment on the undiscussed move above. The definition of the prefixes are in SI, which makes them SI prefixes by, well, definition. Kolbasz (talk) 23:32, 21 March 2013 (UTC)
  • Oppose:Not all of the prefixes discussed in the article are SI prefixes. We have a whole section on disallowed and obsolete prefixes which never were SI. I don't agree that it has no bearing that some prefixes pre-date the SI nor that they are used outside the SI. The SI is a metric system so any SI prefix is also a metric prefix. Thus metric prefix is a broader term. It's useful to use the broader term in that we can include a discussion on things like myria- which is a metric prefix but not an SI one. It's also useful in that we avoid getting tangled up in the fact that these prefixes are used in all versions of the metric system not just the SI. There are kilocalories, hectares, millibars, microergs, etc.; these are all metric but not SI units. Sure the CGPM decided upon the prefixes but the CGPM has been around longer than the SI. JIMp talk·cont 16:45, 22 March 2013 (UTC)
  • Oppose. Jimp's reasoning is cogent and persuasive. Deor (talk) 17:22, 22 March 2013 (UTC)
  • Oppose for same reasons stated by Jimp. Jc3s5h (talk) 18:01, 22 March 2013 (UTC)
  • Oppose - for the same reason as Jimp. Martinvl (talk) 18:56, 22 March 2013 (UTC)

Discussion[edit]

Any additional comments:
The above discussion is preserved as an archive of a requested move. Please do not modify it. Subsequent comments should be made in a new section on this talk page or in a move review. No further edits should be made to this section.

The Greek abbr. "µg," is disfavored as leading to medication errors; the abbreviation mcg is recommended,[edit]

In the metric system, a microgram (µg or mcg) is a unit of mass equal to one millionth (1/1,000,000) of a gram (1 × 10−6), or 1/1000 of a milligram. It is one of the smallest units of mass (or weight) used in a macroscopic context. The symbol "µg" (mu-g) conforms to the International System of Units and is often used in scientific literature, but the United States-based JCAHO recommends that hospitals do not use this symbol in handwritten orders due to the risk that the symbol µ might be misread as the prefix m, resulting in a thousandfold overdose. The abbreviation mcg is recommended instead.[1]

Pronunciation citation[edit]

This sentence doesn't have anything even remotely official backing it up: "When an SI prefix is affixed to a root word, the prefix carries the stress, while the root drops its stress but retains a full vowel in the syllable that is stressed when the root word stands alone."

So, who says this? If it's just a common convention, then why must there be any sort of consistency. One gets the idea that someone just made this up. 08:28, 16 November 2013 (UTC) — Preceding unsigned comment added by 99.56.13.119 (talk)

Possible Volume Incompleteness[edit]

The section on commonly used SI prefixes for volumes only lists millilitres and the like, but somehow does not mention cubic centimetres. Are those really uncommon in English? I am wondering because in German, cubic centimetres are frequently used rather than litre-based units to indicate the size of an empty space inside a vessel, for example in cooking, or for the engine displacement in a car engine. 129.69.215.37 (talk) 14:48, 27 June 2014 (UTC)

I agree. Cubic metres & cubic centimetres are both common enough. Jimp 06:19, 2 July 2014 (UTC)