I bought these boots for my 15 month old toddler. They run small and if you have a chubby baby or even a healthy one, I recommend going one size up. My little guy is nearing the end of size 5 shoes so I ordered a 6. I had to return them for size 7 because I could not get his foot in them. The 7's are still a tight turn to get on but once on they are snug and seem comfortable. This is a good thing to me because we have lost many boots while hiking, etc. These boots are durable and will outlast my little guy.