The point system, used to measure the height of a letter as well as the space between lines ( leading ), is the standard measurement for type. One point equals 1/72 inch or .35 millimeters. Twelve points equal one pica , the unit commonly used to measure column widths.
Typography also can be measured in inches, millimeters, or pixels. (A point is roughly equivalent to a pixel.) Most software applications let the designer choose a preferred unit of measure; picas and points are a standard default.
The horizontal dimension of a letter is its set width . The set width is the body of the letter plus a sliver of space that protects it from other letters. The width of a letter is intrinsic to the proportion of the typeface. Some typefaces have a narrow set width, and some have a wide one.
You can change the set width of a letter by fiddling with its horizontal or vertical scale. This distorts the proportion of the typeface, forcing heavy elements to become thin, and thin elements to become thick. Instead of torturing a letterform, choose a typeface with the proportions you need, such as condensed, compressed, or extended. Type families such as Helvetica, Univers, and Interstate include a variety of widths.