Normally I wear size 11 medium, and a size 11 in this shoe fit well in length. It seems to be a very comfortable shoe with good ventilation. You probably would want to wear these shoes frequently without socks since they are so comfortable and it can be difficult to put them on when wearing socks. My two problems. First, they are narrow for medium feet; their comfort would increase if they came to stretch out in width after wearing for a while. I never got to test this because, secondly, the neoprene inner lining (or whatever the fabric material is) caused a rash on my feet when wearing without socks. So I had to return them.