How Do You Measure Hat Size?
Using a flexible measuring tape, measure the circumference of your head in inches at the place you would comfortably wear a hat. Convert that measurement to hat size using a chart from a company that makes hats or a retailer that sells hats.
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.
Measure your head
Wrap the measuring tape around your head at the largest point over which your hat fits. Put your finger where the tape overlaps, and write down the number of inches.
Convert the inches to hat size
Using a chart from a company, such as Stetson or Lids, convert your measurement to either a numerical hat size or a small, medium, large, extra-large or bigger hat size. Each one of the sizes also comes in adult and youth.
Choose your size
If you prefer looser-fitting hats that are between sizes, go up one size for a more comfortable fit.
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.