Converting Points to Inches in Typography

Wood Type Mixture in a desk drawer

pbombaert / Getty Images

In typography, a point is a tiny measurement that is the standard for measuring font size, leading — which is the distance between lines of text — and other elements of a printed page. There are approximately 72 points in 1 inch. So, 36 points is the equivalent of a half-inch, 18 points is the equivalent of a quarter inch. There are 12 points in a pica, another measuring term in publishing.

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, W3C adopted it for use with cascading stylesheets.

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

You might assume that 72 point type would be an inch tall, but it isn't. The size of the type includes the ascenders and descenders of the typeface. The actual 72 point or 1-inch measurement is of an invisible em square that is just slighting 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.

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 between the sizes of fonts of the same point size. However, so far, most font designers are following the old specifications when sizing their fonts.