Usually more expensive hats require you to know your hat size. In the United States, your hat size is the circumference of your head (measured half an inch above your ears) divided by pi (3.14). The equivalent hat size in the U.K. is an eighth of an inch smaller than the U.S. size.
'''Parts of a Hat'''
* '''Crown''': The part of a hat covering the head.
* '''Brim''': Material that is projected under the crown and continues horizontally around the circumference of the hat.
* '''Peak''': Primarily found on baseball hats and visors, the peak is a stiff projection at the front of the hat that is used to protect eyes from rain and excess sunlight.
* '''Sweatband or hatband''': A ribbon or band running around the bottom edge of the hat.