I knew that it's better to size up with Nike, so that's what I did. I normally wear a women's size 11.5, I ordered size 12 and these shoes fit perfectly! I should say that I hate to wear socks so I don't wear socks with these, but they're so comfortable and stretchy, my feet are happy. I had foot surgery a year ago and it's been hard finding shoes that support my feet well without causing any pain. These fit the bill though.