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' (86cm to 91cm)
S - For Hips 36' to 38' (91cm to 97cm)
M - For Hips 38' to 40' (97cm to 102cm)
L - For Hips 40' to 42' (102cm to 107cm)
XL - For Hips 42' to 44' (107cm to 112cm)