|352.78×10−6 m||352.778 μm|
|US customary units (Imperial units)|
|1.1574×10−3 ft||13.889×10−3 in|
In typography, a point is the smallest whole unit of measure, being a subdivision of the larger pica. It is commonly abbreviated as pt. The point has long been the usual unit for measuring font size and leading and other minute items on a printed page. The original printer's point, from the era of foundry metal typesetting and letterpress printing, varied between 0.18 and 0.4 mm. The defined length of a point varied over time and location until the late 1980s and early 1990s, when the traditional point was supplanted by the desktop publishing point (also called the PostScript point), which was defined as 1⁄72 of an inch (about 0.35 mm). In either system, there are 12 points to the pica.
In metal type, the point size of the font described the size (height) of the metal body on which the typeface's characters were cast. In digital type, letters of a font are designed around an imaginary space called an "em square". When a point size of a font is specified, the font is scaled so that its em square has a side length of that particular length in points. Although the letters of a font usually fit within the font's em square, there is not necessarily any size relationship between the two, so the point size does not necessarily correspond to any measurement of the size of the letters on the printed page.
A measurement in points can be represented in three different ways. For example, 14 points (1 pica plus 2 points) can be written:
- 1P̸2p (12 points would be just "1P̸")—traditional style
- 1p2 (12 points would be just "1p")—format for desktop
- 14pt (12 points would be "12pt" or "1pc" since it is the same as 1 pica)—format used by Cascading Style Sheets defined by the World Wide Web Consortium
French printer's points
- See French units of measurement for the definitions of the units used in this section.
A French law of 1799 defined the metre to be exactly 443.296 French lines—or 3 French feet, 0 French inches and 11.296 French lines, superseding extant definitions that exchanged the dependent and independent parameters. Since the meter is now the standard unit by statute law, this change to a derived unit implicitly defines the modern day Pied du Roi— literally: a French Royal foot— as exactly 9,000⁄27,706 meters (about 0.325 m). Like the English and Roman foot, the French foot also used twelve subdivisions—twelve French-inches. This value is used in the conversions below; also note 12 × 12=122=144—a dozen-dozen, and 12 (French inches) × 144=1728 used below or 123.
The modern typographic point was invented in France by the clergyman Sébastien Truchet (1657–1729). The size he chose was such that 1728 of these made one Pied du Roi— using the 1799 definition, 15,625⁄83,124 mm (or about 0.187972186 mm). To Truchet, a point was defined the other way, there were a dozen-dozen points per French inch—or 1728 or 123 points to a French-Foot.
Pierre Simon Fournier (1712–1768) used a typographic point of about 11⁄864 French Royal inches ≈ 0.345 mm. A close resemblance compared to the modern 72 points to the inch of the American personal computer industry (As referenced above, 1 point = 1⁄72 inches = 25.4⁄72 mm = 0.3527 mm) Fournier's point did not achieve lasting popularity, despite being revived by the Monotype Corporation Ltd. in 1927. Nowadays, Belgium remains one of the few countries to employ Fournier's point. According to the Second Edition of Simon's 1963 Introduction to Typography, type styles such as, Fournier, Plantin and Imprint "are more successful in their smaller sizes".
François-Ambroise Didot (1730–1801) returned to Truchet's idea, but chose a size twice as large. Thus 864 of his points made one Pied du Roi—that is, 15,625⁄41,559 mm ≈ 0.37597151 mm.
This value—somewhat odd due to the divisor, which has the prime factorization 3 × 7 × 1979—was not very flexible for use by typesetters and printers. Though the general size of the Didot point continued to be preferred to that of Truchet, several other printers each chose his or her own value for the point. These are compared below:
- 0.376065 mm (0.0249% larger than Didot's point)—the traditional value in European printers' offices
- 0.376 mm (0.0076% larger)—used by Hermann Berthold (1831–1904) and many others
- 0.37594 mm (0.0084% smaller)—Jan Tschichold (1902–1974), who used 266 points in 100 mm
- 0.375 mm (0.2584% smaller)—proposed in 1975, but hardly adopted
The French National Print Office adopted a point of 0.4 mm exactly, and continues to use this measurement today.
The Didot point has been replaced by the DTP point in France and throughout the world.
Traditional American point system
By the (Kasson) Metric Act of 1866 (Public Law 39-183), the U.S. (survey) foot is 1200⁄3937 m. This is 0.0002% more than 304.8 mm, which is the length of the 1959 foot, used below. A typographic foot contains 72 picas or 864 points.
- Nelson C. Hawks, in 1879, used a printer's foot of a statute foot decreased by 0.375%. Therefore, the traditional ratio 7200⁄7227 (which reduces to 800⁄803) places Hawks’ point at 0.013 837 inch, or about 0.35146 mm.
- A second definition was proposed whereby there were exactly 996 printer's points (= 83 picas) in 350 mm, which made the printer's point about 0.013 848 867 inch ≈ 0.351405622 mm.
- Finally, Lawrence Johnson stated in a third definition of printer's foot that it should be 249⁄250 (99.6%) English foot. This means that the Johnson's typographical point was 0.0138
3inch, and was then converted by the 1959 value to 0.3513 6mm.
In 1886, the Fifteenth Meeting of the Type Founders Association of the United States approved the so-called Johnson pica be adopted as the official standard. This makes the traditional American printer's foot measure 11.952 inches (303.6 mm), or 303.5808 mm exactly, giving a point size of approximately 1⁄72.27 of an inch, or 0.3515 mm.
Like the French Didot point, the traditional American printer's point was replaced in the 1980s by the current computer-based DTP point system.
Current DTP point system
The desktop publishing point (DTP point) is defined as 1⁄72 of the Anglo-Saxon compromise inch of 1959 (25.4 mm) which makes it 0.0138 inch or 0.3527 mm. Twelve points make up a pica, and six picas make an inch.
This system was notably chosen by John Warnock and Charles Geschke when they created Adobe PostScript, by Apple as the display resolution for the original Macintosh, and for the LaserWriter that launched the desktop publishing industry. Therefore, the DTP point is sometimes called the PostScript point.
Traditional point-size names
Fonts originally consisted of a set of moveable type letterpunches purchased from a type foundry. The names for many of the historically popular fonts have become English language shorthand to refer to the corresponding point sizes usually available for letterpress printing:
- 3 pt: Excelsior (US), Minikin (Brit.)
- 4 pt: Brilliant
- 4.5 pt: Diamond
- 5 pt: Pearl
- 5½ pt: Agate (US), Ruby (Brit.)
- 6 pt: Nonpareille
- 6½ pt: Minionette (US), Emerald (Brit.)
- 7 pt: Minion
- 8 pt: Brevier, Petit or small text
- 9 pt: Bourgeois or Galliard
- 10 pt: Long Primer, Corpus or Garamond (c.f. Garamond)
- 11 pt: Small Pica or Philosophy
- 12 pt: Pica
- 14 pt: English, Mittel or Augustin
- 16 pt: Columbian (US), Two-line Brevier (Brit.)
- 18 pt: Great Primer
- 20 pt: Paragon
- 21 pt: Double Small Pica
- 22 pt: Double Small Pica (US), Double Pica (Brit.)
- 24 pt: Double Pica (US) Two-line Pica (Brit.)
- 28 pt: Double English (US), Two-line English (Brit.)
- 30 pt: Five-line Nonpareil (US)
- 32 pt: Four-line Brevier (US)
- 36 pt: Double Great Primer (US), Two-line Great Primer (Brit.)
- 44 pt: Meridian (US), Two-line Double Pica (Brit.), or Trafalgar
- 48 pt: Canon or four-line
- 60 pt: Five-line Pica
- 72 pt: inch
Note that the point size correspondences given here are approximate—often, especially for the smaller ones, the exact size of the original, physical font would vary from foundry to foundry and from country to country. For example, metal type sets that were called Agate are known to have ranged from 5 points up to 5.8 points. Note also that some of the sizes given are no longer considered part of the "traditional scale", such as 44 point type.
Correspondence to Chinese font sizes
|Chinese size name||Translation||Equivalent point size|
|chū (初)||"initial"||42 points|
|xiǎo chū (小初)||"small initial"||36 points|
|yī (一)||"one"||26 points|
|xiǎo yī (小一)||"small one"||24 points|
|èr (二)||"two"||22 points|
|xiǎo èr (小二)||"small two"||18 points|
|sān (三)||"three"||16 points|
|xiǎo sān (小三)||"small three"||15 points|
|sì (四)||"four"||14 points|
|xiǎo sì (小四)||"small four"||12 points|
|wǔ (五)||"five"||10.5 points|
|xiǎo wǔ (小五)||"small five"||9 points|
|liù (六)||"six"||7.5 points|
|xiǎo liù (小六)||"small six"||6.5 points|
|qī (七)||"seven"||5.5 points|
|bā (八)||"eight"||5 points|
- Phinney, Thomas. "Point Size and the Em Square: Not What People Think". Phinney on Fonts. Retrieved 20 August 2013.
- "15 Fonts". Cascading Style Sheets Level 2 Revision 1 (CSS 2.1) Specification W3C Recommendation 07 June 2011. Retrieved 20 August 2013.
- Tucker, H. A. (1988). "Desktop Publishing". In Ruiter, Maurice M. de. Advances in Computer Graphics III. Springer. p. 296. ISBN 3-540-18788-X.
- Spring, Michael B. (1991). Electronic printing and publishing: the document processing revolution. CRC Press. p. 46. ISBN 0-8247-8544-4.
- Theodore Rosendorf (2009). The typographic desk reference: TDR. Oak Knoll Books. p. 25.
- Ken Lunde (1999). CJKV information processing. O'Reilly Media, Inc. p. 340.
- Romano, Frank (Summer 2009). "The History of the Typographic Point" (PDF). APHA Newsletter (171): 3–4.