Measure around the top edge of the waistband to get the waist circumference.
Men's Bottoms Product Measuring Guide
Measuring Guide
A.Waist
B.Hip
Measure the horizontal width at the widest part of the hips (with the pants laid flat), double the measurement for the full hip circumference.
C.Outseam
Measure from the top of the waistband to the bottom hem of the pant leg.
D.Inseam
Measure from the crotch seam to the bottom hem along the inner side of the pant leg.