I am using Google font Open Sans and if I set the font to font-size 11px it looks big for the text I need and if I set it to 10px it looks small so I tested just for fun and
Use percentage instead, you won't get the same size on different displays/browsers, but you should get more control over the size of your text.
e.g: font-size: 98%;
font-size: 98%;
This article may help.