|Unit system||typographic unit|
|metric (SI) units||0.3528 mm|
In typography, the point is the smallest unit of measure. It is used for measuring font size, leading, and other items on a printed page. The size of the point has varied throughout the history of printing. Since the 18th century, the point's size has varied from 0.18 to 0.4 millimeters. Following the advent of desktop publishing in the 1980s and 1990s, digital printing has largely supplanted the letterpress printing and has established the DTP point (desktop publishing point) as the de facto standard. The DTP point is defined as of an international inch (about 0.353 mm) and, as with earlier American point sizes, is considered to be of a pica.
In metal type, the point size of the font described the 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.
The point was first established by the Milanese typographer, Francesco Torniella da Novara (c.1490 - 1589) in his 1517 alphabet, L'Alfabeto. The construction of the alphabet is the first based on logical measurement called "Punto," which corresponds to the ninth part of the height of the letters or the thickness of the principal stroke.
A measurement in points can be represented in three different ways. For example, 14 points (1 pica plus 2 points) can be written:
|Truchet||1694||? 188||? 0.007 400 48|
||1976||= 250||? 0.009 843||=|
|Fournier||1737||? 345||? 0.013 582 677|
|Johnson, ATA||1886||= 351.36||= 0.013 833||=|
|Japan||1962||= 351.4||? 0.013 835|
|variant[who?]||? 351.406||? 0.013 835|
|Hawks||1879||? 351.456||= 0.013 837|
||= 351.459 80||? 0.013 837||=|
||1984||= 352.7||= 0.013 888||=|
||1975||= 375||? 0.014 764||=|
|Tschichold||? 375.94||? 0.014 801||=|
|Didot||1770||? 375.97||? 0.014 802|
|Berthold||= 376||? 0.014 803||=|
||? 376.065||? 0.014 806|
||1997||= 376.296||= 0.014 8||=|
||? 376.682||= 0.014 83|
|L'Imprimerie nationale||= 400||? 0.015 748|
There have been many definitions of a "point" since the advent of typography. Traditional continental European points at about 375 µm are usually a bit larger than English points at around 350 µm.
The Truchet point, the first modern typographic point, was of a French inch or of the royal foot. It was invented by the French clergyman Sébastien Truchet. During the metrication of France amid its revolution, a 1799 law declared the meter to be exactly 443.296 French lines long. At 9000 lines or 16 inches per foot, this established a length to the royal foot of or ca. 325 mm, which made the Truchet point equal to mm or about , although it has also been cited as exactly 188 µm.
The Fournier point established by Pierre Simon Fournier in 1737  was about French inches or (by 1799) 345 µm. This is very close to the present international point, but Fournier's point did not achieve lasting popularity despite being revived by the Monotype Corporation in 1927. It became standard in Belgium.
The system of Fournier was based on the Paris foot, 1 foot = 12 paris inches = 12 * 12 = lignes = 12 * 12 * 12 points. Two of these points became the Fournier-point. Fournier did cast his type on multiples of 3 points Fournier.
12 point Founier equaled 11 point Didot, because of this the Fournier system was later called "median-system". This name "median" was used for type at 11 point.
Approximations were subsequently employed, largely owing to the Didot point's unwieldy conversion to metric units. (The divisor of its conversion ratio has the prime factorization of 3×7×1979.) Values included Hermann Berthold's 376 µm point and Jan Tschichold's (266 points to 100 mm). Due to the definition in TeX of 1157 dd = 1238 pt, the slightly larger became a common value.
TeX also supports a new Didot point (nd) at mm or 375 µm, and cites a 1978 redefinition for it. The French National Print Office adopted a point of mm or 400 µm exactly[when?] and continues to use this measurement today. Japanese and German standardization bodies instead opted for a metric typographic base measure of exactly mm or 250 µm. It is called Q in Japanese after the initial letter of quarter millimetre. Due to demand by Japanese typesetters, CSS adopted Q in 2015.
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A typographic or printer's foot contains 72 picas or 864 points. The Metric Act of 1866 established a legal ratio of between the foot and the meter. This is 0.0002% more than 304.8 mm, the length of the international foot established by the 1959 International Yard and Pound Agreement.
The Hawks point was established by Nelson Hawks in 1879, based on a printer's foot reduced by 0.375% from the standard foot of his time. It had a value of (about ). A variant was proposed[by whom?] to be exactly 83 picas or 996 points in 350 mm (ca. ), giving it a value around .
The Johnson point was established by Lawrence Johnson in the mid-1800s based on a printer's foot as large as the standard foot (11.952 inches or 0.996 foot). It thus had a value of 0.01383 inch. The 15th meeting of the Type Founders Association of the United States (ATA) approved the "Johnson pica" as its official standard in 1886, hence the alias ATA point. Following the 1959 standardization of the foot, this meant the American printer's foot was 303.5808 mm exactly and its point became 351.36 µm.
This size was approximated as exactly of the modern inch by Donald Knuth for the default unit of his TeX computer typesetting system and is thus sometimes known as the , which is 351.45980 µm, and exactly of the PostScript point (bp in TeX).
Like the French Didot point, the traditional American printer's point was largely replaced by the DTP point system.
The desktop publishing point (DTP point) or PostScript point is defined as or 0.0138 of the international inch, making it equivalent to 352.7 µm. Twelve points make up a pica, and six picas make an inch. A separate typographic or printer's foot is not needed anymore.
This specification was developed by John Warnock and Charles Geschke when they created Adobe PostScript. It was adopted by Apple Computer as the standard for the display resolution of the original Macintosh desktop computer and the print resolution for the LaserWriter printer.
Fonts originally consisted of a set of moveable type letterpunches purchased from a type foundry. As early as 1600, the sizes of these types--their "bodies"--acquired traditional names in English, French, German, and Dutch, usually from their principal early uses. These names were used relative to the others and their exact length would vary over time, from country to country, and from foundry to foundry. For example, "agate" and "ruby" used to be a single size "agate ruby" of about 5 points; metal type known as "agate" later ranged from 5 to 5.8 points. The sizes were gradually standardized as described above. Modern Chinese typography uses the following names in general preference to stating the number of points. In ambiguous contexts, the word hào (t ?, s ?, lit. "number") is added to the end of the size name to clarify the meaning.
Note that the Chinese font sizes use American points; the Continental systems traditionally used the Fournier or Didot points. The Fournier points, being smaller than Didot's, were associated with the names of the Didot type closest in size rather than identical in number of points.
|Point||American system||Continental system||Chinese system|
|2||Saxon||Non Plus Ultra
|Non plus ultra
|22||Double Small Pica||Gros-parangon||?||Èr||"Two"|
|24||Double Pica||Palestine||Doppelcicero||Dubbele cicero
|28||Double English||Petit-canon||Doppelmittel||Dubbele mediaan|
|32||Double Columbian||Kleine Kanon
|36||Double Great Primer||Trismégiste||Kanon
|42||Seven-line Nonpareil||Große Kanon||Grote Kanon||?||Ch?||"Initial"|
|60||Five-line pica||Große Missal||Sabon|
|66||Große Sabon||Grote sabon|
|100||Moyenne de fonte|
|108||Nine-line pica||Imperial||9 cicero|
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