This is for titles.

Bodies and large amounts of text should be 16px.

http://www.smashingmagazine.com/2011/10/07/16-pixels-body-co...

If I need to put any amount of effort into reading your site then you are doing it wrong.

Also, open up the dev tools for this article and set the font to 16px. You will see how much better it looks and how easy it is to read.