To be on the safer side, please do this. Really, most snow boots run in sizes. So, when selecting a snow boot for your toddler, please do size up. You might consider selecting a relatively larger size for your toddler's feet. It’s all in a bid to accommodate any unforeseen size issue. More so, your toddler would most likely wear socks with snow boots. In order to then accommodate the socks and still maintain comfortability, size up your toddler winter boots. Snow boots for toddler girls and boys usually have this size issue, so size up. You would safe yourself time and extra cost!