With all the discussion of ems for font sizes this week, I thought it appropriate if I told you about a neat tool that will help you set the default font size so that you can use ems and still have a good idea of how big the font will display on the screen. Ems don't have an absolute size, but are rather based on the value of the font size in the browser or parent elment. So determining how big an em is can be difficult. But the Em Calculator will help you choose ems that are based on a default size that you set. You put in the size in pixels you want, and the em calculator will tell you how many ems that is (based on a standard text size of 16px).