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In typography, a point is the smallest 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 letter press printing, varied between 0.18 and 0.4 mm depending on various definitions of the foot. By the end of the 19th Century, it had settled to around 0.35 to 0.38 mm, depending on one’s geographical location.
In the late 1980s to the 1990s, the traditional point was supplanted by the desktop publishing point (also called the PostScript point), which was defined as 72 points to the inch (1 point = 1⁄72 inches = 25.4⁄72 mm = 0.3527 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, 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" meaning "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.)
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, superseding extant definitions which 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.
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 0.188 mm). To Truchent, 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 ≈ 0.376 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:
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.
By the (Kasson) Metric Act of 1866 (Public Law 39-183), the US (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.
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.
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 sometimes called the TeX point.
Like the French Didot point, the traditional American printer’s point was replaced in the 1980s by the current computer-based 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), it is approximately 0.0139 inch or 0.3528 mm. Twelve points make up a pica, and six picas make an inch.
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.
The following names were often used in the English-speaking world for the point sizes usually available for letterpress printing[1][2]:
Note that the point sizes given here are approximate—often, especially for smaller ones, 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 44 point type.[3]
In China, point size is not used much; instead the following Chinese size names are used (e.g. in the Chinese version of Microsoft Word):
| 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 |
The character "号" in simplified Chinese or "號" in traditional Chinese (pinyin hào, English: "size") is appended to the Chinese name when it is not obvious that a font size is being referred to.
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