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Typographic point

Point
Unit system typographic unit
Unit of length
Unit conversions
1 point in ... ... is equal to ...
   typographic units    1/12 picas
   imperial/US units    1/72 in
   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 172 of an international inch (about 0.353 mm) and, as with earlier American point sizes, is considered to be 112 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.


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