Supportsoft Glossary

Measuring X-Height

X-Height is the height of a typeface's lowercase letters, excluding ascenders and descenders. It heavily influences how legible a font appears at small sizes.

The x-height is exactly what it sounds like: the height of the lowercase letter "x." It sounds like a trivial detail, but it’s actually a dealbreaker for web fonts. This measurement dictates how big the "core" of the letters (like a, c, e, o) feels.

Two fonts at the same point size (say, 16px) can look totally different based on their x-height. A font with a tall x-height looks bigger and clearer on mobile screens because the letters are more open. That’s why we prefer fonts like Roboto or Arial for interfaces—they maximize that vertical space. A short x-height might look elegant, but at small sizes, it becomes a squint-test.