Let me start by saying that I really don't like shoes. If I can walk barefoot, I will. When I wear shoes, I stick to "minimalist" shoes. Any kind of arch irritates my foot. I wear an 8.5 and ordered medium. The average size is 11 inches from heel to toe and 4 inches wide at the widest point. I've been wearing them without socks all day for the past 5 days. When I first put them on I thought they might be too big because there was about 1/2 inch play at the end. But now they've actually molded down to the soles of the feet and the game has shrunk a bit. My feet don't sweat in them much, I know other reviewers have had this issue, but I've never had a problem with sweaty feet. They are flat on the inside. If you are looking for an amazing leg brace these are not for you. If you want to feel barefoot with a little protection on the soles, this is what you're looking for. **UPDATE: November 17, 2016** I wear them to work almost every day and am swapping them out for the second black pair I ordered (I work with kids so I can dress a little more casually). The original pair started smelling, apparently my feet were REALLY sweating a little in them. The shoes don't smell, but these really started to smell funny. I sprayed Odor Eater on it and am thinking of trying thin socks as they absorb the sweat. They are holding up very well, but the outsole shows signs of wear. Overall I'm still very happy with them.**UPDATE: January 31, 2017**My third pair arrived today. The original blue ones I ordered are worn out. The stitching on the suede at the top parted. Can't really complain, I've been wearing them EVERY DAY since I bought them. For this third pair, I went for the small size. I normally wear a size 8.5 and according to the size chart I should wear medium fit kicks. There was a little play in the heel and toe of the middle shoe so I decided to test the small ones. There is less play in the heel and toe box compared to a mid-range shoe, but my big toe doesn't touch the front of the shoe. If I had ordered the little ones as a first pair, they would have been ok (for me). So if you are 8.5 and want a tighter fit go for the small, if you want some freedom and toe room go for the medium. The size of 9 feet does not fit in the small.