A monospaced font, also called a fixed-pitch, fixed-width, or non-proportional font, is a font whose letters and characters each occupy the same amount of horizontal space. This contrasts with variable-width fonts, where the letters and spacings have different widths. For example, the two high-use letters "I" and "E" do not need the same footprint. Both letters differ in center-to-next-letter edge (and center-to-center) spacing distance needs (margins) in variable width fonts. The variable that changes is offset from what would otherwise be monospaced centering. In a modern proportional font, every dimension can be scaled and changed, but such sizing mathematically must still maintain monospacing or variable spacing.

Note that this article generally assumes Western (Latin-based, Cyrillic, or Greek) writing systems. East Asian rules of typography, for example, require CJK fonts to be always monospaced at least as far as the main characters for writing words (i.e. not punctuation) are concerned. Other scripts vary in their use of monospaced fonts.