Converting Points to Inches in Typography

72 is the starting point

Wood Type Mixture in a desk drawer

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In typography, a point is the standard unit of measurement for font size, leading, and other elements of a printed page. Approximately 72 points make up 1 inch. So, 36 points are the equivalent of a half-inch, 18 points equal a quarter-inch, and so on. There are 12 points in a pica, another measuring unit in publishing.

Leading (pronounced /ˈlediNG/) is the distance between lines of text.

The Size of the Point

The size of the point has varied over the years, but modern desktop publishers, typographers, and printing companies use the rounded desktop publishing point (DTP point), which is 1/72 of an inch. The DTP point was adopted by the developers of Adobe PostScript and Apple Computer in the early '70s. In the mid-'90s, the World Wide Web Consortium (W3C) adopted it for use with cascading stylesheets.

Some software programs allow you to choose between the DTP point and the measurement in which 1 point equals 0.013836 inches, and 72 points equal 0.996192 inches. The rounded DTP point, however, is the better option to choose for desktop publishing work.

You might assume that 72-point type would be 1 inch tall, but it isn't. The size of a font includes the ascenders and descenders of the typeface. The actual 72-point (1-inch) measurement is of an invisible em square that is just slightly larger than the distance from the tallest ascender to the lowest descender in the font. This makes the em square a somewhat arbitrary measurement, which explains why all type of the same size doesn't look the same size on the printed page. If the ascenders and descenders are designed at different heights, the em square varies — substantially, in some cases.

Typography terms

Originally, point size described the height of the metal body on which the type character was cast. With digital fonts, the invisible em square height is a choice by the font designer, rather than an automatic measurement extending from the tallest ascender to the longest descender. This may eventually lead to even more disparity among the sizes of fonts of the same point size. However, most font designers follow the old specifications when sizing their fonts.