Pica (unit of measure)

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A pica, (IPA: ['paɪkə]), is a unit of measure in typography. It corresponds always to 1/72 of its respective foot and so to 1/6 inch. There are 12 points in the pica.

The pica originated around 1785 when Françoise-Ambrose Didot (1730-1804, son of French printer François Didot), refined the typographic measuring system created by Pierre Simon Fournier le Jeune (1712-68). He replaced the traditional typographic measurements of cicéro, Petit-Roman, and Gros-Text with such measurements as "ten-point", "twelve-point", etc. for his typographic designs.

In the history of printing until the contemporary period, three different picas were used:

The French pica of 12 Didot's points, also called cicéro is generally: 12 x 0.376 = 4.512 mm or about 0.177 638 inch.

The traditional American printer's system uses a point of 0.013837 in (1/72.27 in). Thus a pica is 0.166044 in (4.2175 mm).

The current computer pica is defined as 1/72 of the Anglo-Saxon compromise foot of 1959, i.e. 4.233 mm or 0.166 inch. This pica was notably promoted by Adobe PostScript and nowadays dominates in the printing industry, just like in home computing and its printers.

A measurement in picas is usually represented by placing a capital P with a top-right to left-down slash beginning in the upper right of the round portion of the "P" and ending at the lower left of the upright portion of the "P"; essentially drawing a "/" through a "P".^{[citation needed]} Likewise, points are represented by placing the number of points before a small p, such as 5p for "5 points," 6P2p for "6 picas and 2 points," or 1P1 for "13 points" which is converted to a mixed fraction of 1 pica and 1 point.^{[citation needed]}

Well known publishing applications such as Adobe InDesign and QuarkXPress represent pica measurements by placing whole picas to the left of a small 'p', following by points, as in: 5p6, which would indicate 5 picas and 6 points, or 51/2 picas.

Note that all of these definitions differ from the “pica” setting on typewriters, which means a type size of ten characters per horizontal inch.