Here's how to determine your correct cap size.

With a tape measure, measure the widest part of your head, just above the ears and eyebrows, to the nearest 1/8th inch.
 

 

Head measurement = Cap Size
Inches 20 1/2 = cap size 6 1/2
Inches 20 3/4 = cap size 6 5/8
Inches 21 = cap size 6 3/4
Inches 21 1/2 = cap size 6 7/8
Inches 22 = cap size 7
Inches 22 1/2 = cap size 7 1/8
Inches 22 3/4 = cap size 7 1/4
Inches 23 = cap size 7 3/8
Inches 23 1/2 = cap size 7 1/2
Inches 24 = cap size 7 5/8
Inches 24 3/8 = cap size 7 3/4
Inches 24 7/8 = cap size 7 7/8
Inches 25 1/8 = cap size 8
Inches 25 3/8 = cap size 8 1/8