Typographic Scale

A typographic scale is a small, deliberately chosen set of font sizes — usually related by a ratio — with each size paired with the line height, letter spacing, and weight appropriate to it. Constraining sizes to a scale is what makes a document look composed rather than assembled.

The pairings matter as much as the sizes. Leading (line height) should tighten as type gets larger: body text wants generous leading for readability, display type wants tight leading or it falls apart into disconnected lines. Tracking (letter spacing) moves in the opposite direction, opening slightly for small uppercase text and tightening for large display. Treating these as independent knobs rather than properties of a scale step is how interfaces end up with headings that read as accidents.

Scale is also contextual. Application chrome — toolbars, menus, controls — generally wants a compact scale that is quite different from content typography, and menus should match the control that opened them. Mixing content scale into chrome makes an interface feel bloated; mixing chrome scale into content makes it feel cramped.

Measure line length too. Readability falls off sharply beyond roughly seventy-five characters, and in a terminal or a narrow column it must be derived from the available width rather than assumed. See Terminal User Interface.