Estimating the x-height of a font

This page can be used to get an estimate of the relative x-height (aspect ratio) of a font. Specify a font and a guess of x-height in pixels for a font size of 1,000 pixels. The vertical bar to the left of the letter x (displayed in that font size) will then occupy the height you specified. The initial guess is 500. Once the vertical bar is as tall as the letter, you have found a rather accurate estimate for the x-height of the font. For example, if height 466 gives the match, then the relative x-height of the font is 0.466.

If you specify a font that does not exist in your system (e.g., mistype the font name), the x appears in the Courier font, to make it easier to recognize that there is a problem.

The test on this page only works when JavaScript is enabled. Your browser has JavaScript disabled or does not support JavaScript. You can still view the test results, links, and comments.

Some results
Arial	0.519
Arial Unicode MS	0.518
Calibri	0.466
Cambria	0.466
Candara	0.463
Code2000	0.444
Comics Sans MS	0.532
Courier	0.425
Courier New	0.423
Garamond	0.384
Georgia	0.481
Helvetica	0.523
Tahoma	0.545
Times New Roman	0.448
Trebuchet MS	0.523
Verdana	0.545

For comparison:

Compute the ‘normal line-height’ and the ‘aspect value’ of the installed fonts; a page based on programmatic calculation of the x-height, agreeing with the results shown above
x-height, font-size-adjust test page by Bruno Fassino
Aspect values for web fonts by Barry Pearson
Description of font-size-adjust in CSS 2.0. The property was removed from CSS 2.1 due to lack of implementations. However, Firefox has implemented it. The specification claims that Verdana has aspect ratio of 0.58, contrary to other sources.

Although the results seem to indicate that the CSS 2.0 specification was in error in this matter, it is possible that its figures apply to some special circumstances. Depending on the implementations, there might be different relative x-heights for a font in different sizes, even though this may sound illogical. Perhaps results are intentionally different, because small font sizes impose their own requirements, so that the x-height is larger than in other fonts, to keep all letters minimally legible. I am indebted to Bruno Fassino for the observation of such possibilities as well as other notes on this theme.