My 13 month old son has very chunky thick feet (of normal length) and I bought the 18-36 month size, he's wearing them now. They are a little big which means they are true to size since he's not 18 months yet, they look like they will fit at least until 24 months. They are NOT too tight on his calf which is usually a big problem with baby socks. They DO NOT leave those elastic marks on him. They are soft and thick so he can fit a slightly larger shoe and fit his normal shoe size as well. They're very cute and bright. They also don't make his feet sweat like a lot of socks do if they're not 100% cotton. I think these are like 70% cotton though I'm not SURE, but they are kind to his feet. For this price they are worth trying to see if they are good for your lil one as well  =o)