size Biceps Forearm 10cm above knee cap Calf
XS 28 - 29 24 - 25 37 - 39 34.5 - 35.5
S 30 - 31 25.5 - 26.5 40 - 42 36 - 37
M 32 - 33 27 - 28 43 - 45 37.5 - 38.5
L 34 - 35 28.5 - 29.5 46 - 48 39 - 40
XL 36 - 37 30 - 31 49 - 51 40.5 - 41.5

Measure the circumference of your arm [1] approx 10 cm / 3.9 inches above the center of your elbow bone. Measure the circumference of your thigh [2], taken 10 cm / 3.9 inches above the center of your knee cap.