Measure the widest part of your head with a tape measure. Place the tape measure an index finger above the ear, bring it across the mid forehead, completely circling the head. Note the inches, and see the chart above. Please measure without any free space. If your measurement falls between sizes, choose the next largest size. If you have to order the next largest size, you should definately order some FedoraFelts.  Incorrect fit is very possible if extreme care is not taken.   Heads come in all kinds of shapes and sizes, and fitting a hat is not an exact science.  However, with the FedoraFelts(tm) or with the The Hat Jack you can make your hat fit perfectly.