The Real Meaning of font-size: 80%
CSS font "sizes", for simplicity, refer only to height. However, everything we see on a computer display has two dimensions, height and width. Any text we reduce by 20%, we make both 20% shorter, and 20% narrower. The net reduction in visible area from specifying font-size: 80% is therefore 36%.
The quick brown fox jumped over the sleeping dog. 80%
The quick brown fox jumped over the sleeping dog. 100%
The quick brown fox jumped over the sleeping dog. 16px
The quick brown fox jumped over the sleeping dog. 20px
