Average head size measurements range from 21" (53cm) to 23" (58cm) in half sizes.
This is the back to front measurement and usually measures 9 1/2" (24cm) to 10 1/2" (26. 5cm).
This is the side to side measurement and usually measures 10" (25. 5cm) to 10 1/2" (26. 5cm).
