What size shoes for most 12-18 month olds?

Jessica • Mom of 2 boys, 1 girl🧒🏼👦🏼👦🏼26 years young. Engaged💝💍

Struggling to find shoes/boots that fit. Bought my daughter size 5 boots cuz they were snug when I tried them on her in the store. Also didn’t want them falling off. Now that shes worn them a couple times they are so loose and fall off constantly. What size are most babies this age?