All Rey to Z hats adjust 1-2 inches both smaller and bigger. The inches listed below are the average size of the hat before it is adjusted:Baby Hat (0M-12M) - 19 inches (metal buckle)Toddler hat (1Y-4Y) - 21 inches (metal buckle)Child hat (5Y-10Y) - 25 inches (metal buckle)Adult hat – 25 inches (metal buckle)