Pitch is the number of characters and spaces in one inch (2.5 cm) of running text, that is, characters per inch (abbreviated cpi). The pitch is most often used as a measurement of font size of typewriters as well as printers.
The relation between pitch font size and typographic font size (points) is usually inverse: a 12-pitch typewriter font is equal in height to 10-point typographic font, while a 10 pitch-typewriter font is equal in height to 12-point typographic font. However, this relation is not obligatory, e.g., a 12-pitch font with a smaller x-height can have the same body height as a 10-pitch font, thus creating a text with increased line spacing.
The most widespread fonts in typewriters are 10 and 12 pitch, called pica and elite, respectively. There may be other font styles with various width: condensed or compressed (17–20 cpi), italic or bold (10 pitch), enlarged (5–8 cpi), and so on.
In typography a similar concept is applied in the process of copyfitting: a number of characters per pica (cpp), a pica being a sixth of an inch. As books are most often printed with proportional fonts, cpp of a given font is usually a fractional number. For example, an 11-point font (like Helvetica) may have 2.4 cpp, thus a 5-inch (30-pica) line of a usual octavo-sized (6×8 in) book page would contain around 72 characters (including spaces).
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