To identify your waist-size, learn the contour of your torso from right and left. Where it bends, that is your waist. Measure around your waistline, keeping the tape secured tightly to your body.
Stand up straight with your feet together and the legs straight. Measure around the fullest section of your hips.
Ask someone else to take this measurement. Stand with your legs and torso completely straight. Place the tape at the center of your bust, keeping the tape straight until you reach the seam of your pant.