The size seems true to me. I wear a 10 /2 D shoe and the 10 fits without my feet hanging off the back. What surprised me a bit is that the bottom of the slipper is covered with a nylon cloth like material and they don't grip quite as well as I would like. For walking it hasn't been an issue but there are certain calf stretches that I have to do and I can't do them on the wood or tile floors anymore because my foot slides away. Fortunately we still have one carpeted room. Otherwise I am fairly pleased they are a lot cooler than the moccasin style that I've worn for years, which is what I was hoping for.