font-size-adjust

The font-size-adjust property allows you to make alternative fonts, such as the second and subsequent fonts in your font stack more legible by adjusting the ratio of their font size to their x-height. The higher this value is (in general) the more legible the font will be at smaller sizes.

• CSS 2 (but was removed from CSS 2.1)
• CSS 3 (it was brought back in CSS3)

font-size-adjust: <number> | none | inherit;

• number—the aspect ratio, usually of your first choice font. This is then applied to second choice fonts as a scaling factor using the following formula:

  y * (a/a') = c

  • y = the font-size of your first choice font
  • a = the aspect value or number in the font-size-adjust property
  • a' = the aspect value of the available font
  • c = the font-size to apply to the available font
• none—no adjustment should be made to the font size
• inherit—the font size adjustment should be the same as the parent element.

none

All elements.

This property is inherited.

• Firefox 3+

If 14px Verdana (with an aspect value of 0.58) was unavailable and an available font had an aspect value of 0.46, the font-size of the substitute would be 14 * (0.58/0.46) = 17.65px. (from W3C)

• The legibility of a font is dependant on more than the font-size but also on the relationship between the size and the x-height.
• The higher the aspect ratio is, the more legible a font will be at smaller sizes.
• Font substitution that relies on font-size alone may rapidly render a page illegible.

More font-size-adjust Information

• How to Use the font-size-adjust Property
• Aspect Ratio Table of Common Fonts

Related Style Properties

• font-size
• font
• font-family
• font-style
• font-variant
• font-weight

Return to the CSS Style Properties Library