x-height

x-height is the height of the lowercase letters, disregarding ascenders or descenders, typically exemplified by the letter x. The relationship of the x-height to the body defines the perceived type size. A typeface with a large x-height looks much bigger than a typeface with a small x-height at the same size.

The typefaces with large x-height render well in busy backgrounds by allowing counters of an optimum size which aid legibility. Especially, the letters with three horizontal strokes such as a,e,s benefit from higher x-height.

Typefaces with large x-height are more legible when viewed at a distance because the large x-height results in large counters. However, too large x-height can lead to the misrecognition of letters. The x-height should be optimised to get a right balance between the ascender and the counter size keeping in mind the deterioration caused by rounding and irradiation.

  • The impact of x-height ceases to exist width of the letter is small. Hence these two factors should be considered in tandem.

  • In the case of letters with two horizontal strokes (o,z,b,d,p,q) large x-height does not affect the legibility much.

  • Use of large x-height in some cases might lead to misrecognition among the letters if the x-height overpowers the ascenders height (see image ), which usually get suppressed by rounding at the edges because of irradiation thereby decreasing the legibility.

  • Ascenders play a huge role in letter recognition as compared to descenders.

  • x-height does not help if the counters are narrow and strokes merge into each other when viewed at an angle.