One reviewer said the sizing ran small; however, I bought a pair a size larger than I normally wear, wishing to wear double socks with it - but they barely fit with thin "trouser" socks.  I returned them (Amazon made it so easy to do!) and reordered in a size 2 sizes bigger than my normal size, and they work perfect with a pair of thin socks paired with a pair of thick "wooly" socks.  I also have "heavy calves," so buying boots is often an ordeal for me.  After reading another review that said the boots fit legs shaped like mine, I was encouraged to try them.  I'm so happy I did!  Love 'em!