The diagram shows the most appropriate locations to measure your body. Often people will measure at the wrong location and get false results. For example, when measuring your waist, some people take the measurement below the belly button when your natural waistline is located above the belly button! When taking these measurements, make sure the tape is level and is neither too tight nor too loose. Also measure yourself on your bare skin, not over clothes.
If you don't have a cloth tape measure you could use a long piece of cloth (like a ribbon or bathrobe tie) measure yourself with this, then measure the cloth on the floor with a metal tape measure.

Chest: Measure the circumference of your chest. Place one end of the tape measure at the fullest part of your bust, wrap it around (under your armpits, around your shoulder blades, and back to the front) to get the measurement.

Waist: Measure the circumference of your waist. Use the tape to circle your waist (sort of like a belt would) at your natural waistline, which is located above your belly button and below your rib cage. (If you bend to the side, the crease that forms is your natural waistline.) Don’t suck in your stomach, or you’ll get a false measurement.

Hips: Measure the circumference of your hips. Make sure the tape is over the largest part of your buttocks. Because making sure the tape is level back there can be hard, try to do it in front of a mirror.