For the waist, lay your jeans flat and buttoned. Measure the waistband from end to end and multiply this number by two.
For the thigh, measure straight across the leg from the crotch.
For the front rise, start at the end of the crotch seam and measure straight up to the middle of the front waistband.
Knee measurements are taken exactly 13" down from the crotch seam.
For the leg opening, measure across the bottom of the leg at the opening.
Run a measuring tape from the crotch seam to the hem of the pants.