In typography, a point is the smallest unit of measure, being a subdivision of the larger pica. It is commonly abbreviated as pt. The traditional printer's point, from the era of hot metal typesetting and presswork, varied between 0.18 and 0.4 mm depending on various definitions of the foot.
Today, the traditional point has been supplanted by the desktop publishing point (also called the PostScript point), which has been rounded to an even 72 points to the inch (1 point = ^{127}⁄_{360} mm ≈ 0.353 mm). In either system, there are 12 points to the pica.
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A French law of 1799 defined the meter to be exactly 443.296 French lines—or 3 French feet, 0 French inches and 11.296 French lines. Since the meter is now the standard unit, this implicitly defines the Pied du Roi, or French Royal foot, as exactly ^{9,000}⁄_{27,706} meters (about 0.325 m). This value is used in the conversions below.
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}⁄_{83,118} mm (or about 0.188 mm).
Pierre Simon Fournier (1712–1768) used a typographic point of about ^{11}⁄_{864} French Royal inches ≈ 0.345 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."
FrançoisAmbroise 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 ≈ 0.376 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:
Note that the French National Print Office adopted a point of 400 µm exactly, and continues to use this measurement today.
The Didot point has been replaced by the DTP point in France and throughout the world.
By the (Kasson) Metric Act of 1866 (Public Law 39183), the US (survey) foot is ^{1200}⁄_{3937} m. This is 0.0002% more than 304.8 mm, which is the length of the AngloSaxon compromise foot of 1959, used below. A typographic foot contains 72 picas or 864 points.
In 1886, the Fifteenth Meeting of the Type Founders Association of the United States approved the socalled 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 351.5 µm.
This is the size of the point in the TeX computer typesetting system by Donald Knuth, which predates PostScript slightly. Thus the latter unit is commonly called the TeX point.
Like the French Didot point, the traditional American printer’s point was replaced in the 1980s by the current computerbased DTP point system.
The desktop publishing point (DTP point) is defined as 1/72 of the AngloSaxon compromise inch of 1959 (25.4 mm), it is approximately 0.0139 inch or 352.8 µm. Twelve points make up a pica, and six picas make an inch.
The point is the usual unit for measuring font size and leading and other minute items on a printed page. This system was notably promoted by John Warnock and Charles Geschke, the inventors of Adobe PostScript, and therefore it is sometimes also called PostScript point.
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, the body is now an imaginary design space, but is used as the basis from which the type is scaled (see em).
A measurement in picas is usually represented by placing a lower case p after the number, such as "10p" means "10 picas". Points are represented by placing the number of points after the p, such as 0p5 for "5 points," 6p2 for "6 picas and 2 points", or 1p1 for "13 points" which is converted to a mixed fraction of 1 pica and 1 point. (An alternate nomenclature is described in the pica article.)
The following names were often used in the Englishspeaking world for the point sizes usually available for letterpress printing:
Note that the point sizes given here are approximate—often, the exact size would vary from foundry to foundry or country to country. For example, metal type which was called agate has been known to have been from 5 points and up to 5.8 points. Note also that some of the sizes given are no longer considered part of the "traditional scale", such as 15 point type and 44 point type.^{[1]}
In China, point size is not used much; instead the following Chinese size names^{[2]} are used (e.g. in the Chinese version of Microsoft Word):
Chinese size name  Translation  Equivalent point size 

chū (初)  "initial"  42 points 
xiǎochū (小初)  "small initial"  36 points 
yī (一)  "one"  26 points 
xiǎoyī (小一)  "small one"  24 points 
èr (二)  "two"  22 points 
xiǎo'èr (小二)  "small two"  18 points 
sān (三)  "three"  16 points 
xiǎosān (小三)  "small three"  15 points 
sì (四)  "four"  14 points 
xiǎosì (小四)  "small four"  12 points 
wǔ (五)  "five"  10.5 points 
xiǎowǔ (小五)  "small five"  9 points 
liù (六)  "six"  7.5 points 
qī (七)  "seven"  5.5 points 
The syllable 号 (hào, "size") is appended to the Chinese name when it is not obvious that a font size is being referred to.

