To size correctly, measure the circumference of the largest part of your calf. This is not flexed. Sizes Circumference of Calf (in) S < 15 in M 15 - 16 in L 16 - 17 in XL 17 - 18 in 2XL 18 - 19 in 3XL 19 - 20 in 4XL > 20 in