To measure hat size, use a tape measure or a length of string to measure the circumference of the head about 1/8 of an inch above the ears. Charts showing the hat size that corresponds to each circumference are available on VillageHatShop.com and DavidMorgan.com.
When measuring hat size, ensure that the measuring tape or string is reasonably tight, but not as tight as possible. If the string is pulled too tight, the resulting measurement may indicate a hat size that is uncomfortably small for the wearer. If the circumference measurement falls in between hat sizes, the larger of the two is generally the better choice.
Hat sizes should be universal, but exact measurements may vary to a small degree among different manufacturers and styles of hats. If purchasing a hat from a specific hat maker, it is advisable to try on a few different sizes of hats in the store to accurately gauge the optimal size.
The smallest standard hat size is 6 3/4, which corresponds to a head circumference of 21 1/8 inches. The largest standard size is 8 1/8, corresponding to a head circumference of 25 1/2 inches. Not all hat manufacturers carry every hat size. Mass-produced hats are often grouped into sizes small through extra large. In general, a small hat ranges in size from 6 3/4 to 6 7/8.