Kids' shoe sizes can be confusing to navigate. Unlike clothing sizes, your child's shoe size doesn't correspond to their age, unless they're a baby. Baby shoes are listed by age in month. However, you should still measure their feet, since some little ones grow faster than others!
Once your child graduates into kid-size shoes, the sizing system switches to numbers. Sizes 3.5 to 10 are considered little kid shoes. From Size 10.5 onward, you're into big kid sizes. When your big kid outgrows their size 13.5 kids' shoes, the system changes again to adult sizing, and you'll be shopping for a pair of size 1's.