What Is Cap Height? Capital Letter Height in Typography

Cap height is the distance from the baseline to the top of a capital letter. Flat letters such as H, E, T and I show it exactly. Round letters such as O, C and S, and pointed ones such as A, are drawn a little taller (overshoot), so the eye reads them as the same height as the flat ones. Without that correction, round capitals look too small.

Cap height and its neighbours

Along with the baseline, x-height and the ascender and descender lines, cap height defines the zones of a line of type:

Metric	What it measures
Baseline	The line letters sit on
x-height	Top of lowercase letters such as x, a, e
Cap height	Top of flat capitals such as H, E
Ascender height	Top of letters such as b, d, h, l
Descender depth	Bottom of letters such as g, p, y

In many serif text faces the ascenders reach slightly above the cap height, which keeps capitals from looking heavy in running text. In many sans-serif faces the two are almost level. Neither is a rule; each type designer decides.

The ratio between cap height and x-height gives a typeface much of its character. A tall capital over a small lowercase body feels classical; capitals and lowercase of similar scale feel more neutral.

Cap height in lettering

All-capital lettering, as in block letters, signs and graffiti outlines, lives entirely between baseline and cap height. That makes layout straightforward and strict at once. Any wobble in the cap line shows across the whole word. For reliable results:

Rule the baseline and the cap line with a ruler, using a light pencil.
Make the crossbars of E, F and H sit slightly above the centre, so they do not look as if they sag.
Let round letters touch or just pass the lines, instead of stopping at them.
Check the height in a photograph or in a mirror: errors become obvious.

Our bubble letter drawing guide uses the same method for inflated forms, and the how to write in cursive guide shows where capitals sit in school cursive.

Cap height and fancy Unicode text

Capital letters in the Mathematical Alphanumeric Symbols block, such as 𝐇𝐄𝐋𝐋𝐎, are drawn by whichever font the device selects, so their cap height follows that font. Small-cap style text, like the output of a small caps generator, is a different matter: it uses real small-cap letters (for example U+1D00, LATIN LETTER SMALL CAPITAL A) with a height around the x-height, which is why it reads like lowercase text in capital shapes. Not every letter exists in that form, and the missing ones are filled by other characters, as explained on that page.

Common confusions

Cap height is not x-height. One is capitals, the other lowercase.
Cap height is not font size. The size is an em box; the cap height is a fraction of it, usually around 0.65 to 0.75.
Cap height is not ascender height. They are close but separate numbers in a font, and they differ in many serif faces.

Frequently asked questions

How is cap height measured?

It is measured from the baseline to the top of a flat capital such as H, E, I or Z, as these letters have no overshoot. Round capitals like O and C are drawn slightly taller so they look the same height as flat ones, so measuring them gives a slightly larger number.

Are ascenders taller than capitals?

In many typefaces, yes. Letters such as b, d, h and l often rise a little above the capitals, particularly in old-style serif faces such as Garamond. In many sans-serif fonts the ascenders and capitals are nearly the same height. It depends on the design, so check by setting both side by side.

Why does cap height matter for all-caps lettering?

In all capitals, the cap-height is the only height that matters, so the letters form a rectangular block. This makes spacing and layout simple, and makes consistent guidelines crucial: a few millimetres of drift in the top line is far more visible than it is in lowercase writing.

What is the cap-height line in handwriting practice?

It is the guideline marking the top of capital letters. In school cursive sheets the cap line often sits level with the ascender line or a little below it. Using it keeps capitals consistent, so every sentence starts with a letter of the same size.