Use a plastic tape measure. Cloth varieties can stretch out over time and give you distorted measurements.
Position the tape correctly. Don't pull the tape tightly to get a smaller measurement. "Make sure the tape is snug, does not compress your skin and is parallel to the floor," says Maria Kinirons, director of food and nutrition for Weight Watchers North America. Wear thin fabrics -- or better yet, nothing at all.
Breathe normally. Don't suck your breath in or exhale forcefully when measuring your waist or chest.
Look straight ahead. Stand tall with your feet together -- or slightly apart if you're measuring your thighs -- preferably in front of a full-length mirror so you can see the tape's position. Don't slouch to look at your reading. For the most accurate results, ask a family member or friend to help.
Take monthly measurements. Don't measure too often: Readings can change from day to day -- and even at different points in a single day -- based on what you eat and drink. Pick one day a month and measure yourself first thing in the morning. Women should schedule this just before or during their period, when they tend to be more bloated.
Measure at the right place. For your chest, measure around the largest spot, generally at the nipple line. Waist: just above your hipbones, roughly at your belly button. Hips: the widest part of your buttocks. Arms: about 3 inches above the elbow, at the largest point. Thighs: the biggest part of your upper legs.
