Measure around your natural waistline, keeping the tape a bit loose.

Size Waist (inches) Length (inches)
30 (S) 29-30 39-40
32 (M) 31-32 40-41
34 (L) 33-34 41-42
36 (XL) 35-36 41-42
38 (XXL) 37-38 41-42