Characters per inch

Pitch is the number of characters and spaces in one inch 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 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. Though this relation is not obligatory: a smaller in the x-height 12 pitch font can have the body height equal to 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, a 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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