Font Sizes
Following is a handy matrix for those among us who like to indicate HTML (font) sizes in “em”s. All modern browsers use a 16px default font size. Specifying the font-size and line-height in ems (relative to the 16px default font) allows the user to resize the font in the browser and produces the most consistent results across different browsers.
For more about using em’s, read: http://www.alistapart.com/articles/howtosizetextincss
Now, the matrix:
font-size: .625em; = 10px
font-size: .6875em; = 11px
font-size: .75em; = 12px
font-size: .8125em; = 13px
font-size: .875em; = 14px
font-size: .9375em; = 15px
font-size: 1.0625em; = 17px
font-size: 1.125em; = 18px
font-size: 1.188em; = 19px
font-size: 1.25em; = 20px
font-size: 1.313em; = 21px
font-size: 1.375em; = 22px
font-size: 1.438em; = 23px
font-size: 1.5em; = 24px
font-size: 1.563em; = 25px
font-size: 1.625em; = 26px
font-size: 1.688em; = 27px
font-size: 1.75em; = 28px
font-size: 1.813em; = 29px
font-size: 1.875em; = 30px