Hint: For the most accurate results, measure yourself in your underwear.

Chest: Measure around the fullest part of your chest, keeping tape firmly under your armpits and around your shoulder blades.
Waist: Measure around your waist, slightly below your natural waist, where you normally wear your pants. Insert your forefinger between the tape and your body to allow ease in fit.
Hip: Measure around the fullest part of your hips, inserting your forefinger between the tape and your hip to allow ease in fit.
Inseam: Measure a similar pant that fits you well. Measure along the inseam, from the crotch seam to the bottom of the hem.