I have size 1-3 for my 18 month old son and 4-8 for my 3 year old daughter. Both fit great. My 18 month old daughter wears a size 7 shoes and a size 1-3 fits very well. My 3 year old daughter wears a size 9 shoes and a size 4-8 fits well although she could use a size smaller. The socks are very soft, thick and feel warm. To wear these socks with shoes, you need to increase the size of the shoes, otherwise the socks will not fit - they are so thick. The photographs are comparison sizes 1-3 and 4-8.