This range was produced a little small, so if in doubt, go up a size and they should be perfect.
The waist measurement is fairly open, due to the drawstring, so your hip measurement is the best guide:
XS - For Hips 34' to 36' or 86cm to 91cm
S - For Hips 36' to 38' or 91cm to 97cm
M - For Hips 38' to 40' or 97cm to 102cm
L - For Hips 40' to 42' or 102cm to 107cm
XL - For Hips 42' to 44' or 107cm to 112cm