Small (54-57cm)= 21 1/4 in to 22 3/8 in
Medium (57-59 cm)= 22 3/8 in to 23 1/4 in
Large (59-62 cm)= 23 1/4 in to 24 3/8 in
Step 1: Find a measureing tape or something to use as a reference
Step 2: Wrap the measuring tool around your forehead
Step 3: Use the give measurements to find your size