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.Continue Reading
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.
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.
If you prefer looser-fitting hats that are between sizes, go up one size for a more comfortable fit.