If you are curious about your head size, this is an easy way to measure it yourself relatively accurately:
You take a tape measure and start in the middle of your forehead. The tape measure goes right about your ear, pass the thickest part at the back of your head (the top of the ‘bump’ that many people hat), pass above the other ear and come back to the forehead. This is an easy way to measure your head. However, if you have any doubt, I can always do it for you!