Measure once
Wrap a soft tape just above your eyebrows and ears and read the number in cm. Measure twice and take the larger. 53–55 cm is Small (US fitted 6 3/4 to 6 7/8), 56–57 cm Medium (7 to 7 1/8), 58–59 cm Large (7 1/4 to 7 3/8) and 60–62 cm X-Large (7 1/2 to 7 3/4). Adjustable caps fit about 54 to 61 cm.