As recommended by other reviewers, I ordered a whole size bigger.  May not have had to order a whole size but they fit a little big.  Thought if I needed to wear extra socks it would give me more room for that.  Don't seem to need thicker socks.  The boots are very warm and waterproof.  Love them. I had read that it is best to have a little extra room in boots so the feet don't sweat but stay warm so far that has worked for me.