Measure your head at the place where the headband will rest. If your size falls between size order the next larger

20 3/4 Inches = 6 5/8 (SMALL)

21 1/8 = 6 3/4 (SMALL)

21 1/2 = 6 7/8 (SMALL)

21 7/8 = 7 (MEDIUM)

22 1/4 = 7 1/8 (MEDIUM)

22 5/8 = 7 1/4 (LARGE)

23 = 7 3/8 (LARGE)

23 1/2 = 7 1/2 (EXTRA LARGE)

23 7/8 = 7 5/8 (EXTRA LARGE)

24 1/4 = 7 3/4 (EXTRA LARGE)

24 5/8 = 7 7/8 (EXTRA LARGE)