My girls had tiny feet and were in a size 5 for ages, but often needed a 6 to get a wider fit because they have wide feet like DH and I. DS2 is 2.5 and is on his way to a 9! I brought a pair of clarks sandals in a 7E in october thinking they would last the summer but they didn't even last till Christmas. He has big flippers LOL. My niece on the other hand is just over 3, reasonably tall but is only in a size 5