Relative Font Sizes

The em-px-pt-percent font size argument is an old one. Most developers have been oblivious to the argument, but it firmly roots itself in a question of accessibility. Consider the following when understanding font size choices.
  • Latin- and non-Latin-based languages may differ significantly in standard font sizes; due to this, browser support for text sizing is very important
  • IE7 and earlier browsers do not accurately resize pixel- and point-based font sizes when modifying the text size; for this reason, prefer em or % over px/pt
  • IE6 and earlier browsers exagerates ems, compared to %; for this reason, prefer % over ems
Based on this, the least common denominator suggests that percent-based font sizes are ideal and, as such, we are using them within uAKS. The only hope for the future we can really give those of you that are [rightfully] cringing at relative font sizes is that all modern browsers (i.e. Chrome, Firefox, IE8, Opera, and Safari) all handle both absolute and relative font sizes adequately for all accessibility needs brought to our attention. If only we could magically get everyone to upgrade their IE6 and 7 browsers to IE8...

Size Utility


The Size Utility provides a simple way to help migrate from absolute to relative font sizes. The tool supports converting pixels and points to ems and percents. The conversion rates are listed below (i.e. 1 pt = .0625em and 1px = 8.333%). Obviously, you can see here that 1em = 100%.

From \ To Em %
Pt .0625 6.25
Px .083 8.333

There are many tools available online, so feel free to use any tool you're familiar with. If you have recommendations on tools to reference or possibly include, please let us know. As of right now, we're not planning to improve the tool. If you have any ideas that would make this a much more valuable tool -- or you simply believe it's an integral piece of the overall solution -- definitely let us know. Otherwise, if you'd like to check it out, refer to release 0.1 - Open Self-Service, which has the original HiSoftware release. While the prospect of converting this utility to WPF and vastly improving the experience of the original software sounds like a lot of fun, the tool's value is very questionable. If someone would like to donate some time to do the conversion, have at it; we'd love the contribution.


Last edited Nov 6, 2009 at 6:21 PM by flanakin, version 6


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