I don't know if it helps, but my daughter is one year old and 30.5" tall and about 20 pounds (she's always been on the thin side), and these shoes are very big on her.  Having said that, where they are soft and more or less contour to her feet, the largeness of the shoes (I bought 12-18 months) does not seem to keep her from walking in them or playing around. She just started walking and takes as many as 10 steps at a time, and these do not seem to inhibit her movement.  Better yet (for me), they say on.  Really, they do.  Sometimes if it is a particularly cold day, I will put her down for a nap wearing her shoes (they are so soft and comfortable) and she will still have them on when she wakes up.