I read many reviews stating that these fit large, I'm usually somewhere between 10-11 in most brands so I ordered a 10 and they fit well. My heel was slipping slightly in regular socks, but when i tried them on with thicker camp socks, which you'd probably be wearing in the weather these boots are for, they fit much better. I didn't consider sizing down since my toes were already comfortably fitting in the front and one size down would probably be too small. I will say that even though the boots look like they'd be huge at the top, they fit snuggly on my large calves, so if you have more muscular legs you might run into a problem. I can't imagine wearing these with anything thicker than jeans.