Font size is the height of a typeface. Let's first define typographical terms like ascender and descender before moving on to a more detailed explanation.

• Ascender is the vertical stroke found on lowercase letters (b, d, f, h, k, l, t) that extends above the typeface's x-height.
• Descender is the part of a lowercase letter that extends below the baseline.

Font size equals the distance between the top of the ascender height to the bottom of the descender height. Designers usually use points (8, 10, 12, etc.) to measure font size, where 1 point equals 1/72 inch or 0.35 mm.