Booties Size Fit Foot Length 3M 0 to 3 Months up to 3.25" 6M 3 to 6 Months 3.75" 12M 6 to 12 Months 4.25" 18M 12 to 18 Months 4.5" 24M 18 to 24 Months 5" If unsure or in between sizes, we recommend sizing up.