Measure around your waistline where you normally wear your pants with one forefinger between your body and the measuring tape.
Stand with your heels together, keeping tape straight and parallel to the floor. Measure around the fullest part of your hips.
Using a pair of pants that fit you well, measure from the crotch seam to the opening at the bottom of the pant leg. Round the number to the nearest 1/2" to get your inseam length.