This boot runs pretty true to size. I ordered 1/2 size up just in case (thick socks and all) but probably didn't need to do so. This boot is well made and makes my size 10 feet look small! They are extra warm and the first day I had them I walked almost 5 miles in them and though I could tell at the end of the day I had on brand new shoes, no blisters or sores or anything from the extended walking!  Great price on Amazon. I'd buy again.