They don't have a size. They fit like any of the individual pairs of fun printed socks you can get at target. I would say they most comfortably fit people with shoe sizes 5-9. I wear a size 7.5 shoe and I own several pairs of these & they fit me perfectly. I would say they would be too large for anyone with a shoe size smaller than 5 and too small for anyone with a shoe size larger than 9.