Measure around the base of your neck, inserting your forefinger between the tape and your neck to allow ease in fit.
Measure around the fullest part of your chest, keeping tape firmly under your armpits and around your shoulder blades.
Measure around your waist, slighlty below your natural waist, where you normally wear your pants. Insert your forefinger between the tape and your body to allow ease in fit.
Measure a similar pant that fits you well. Measure along the inseam, from the crotch seam to the botton of the hem.