Measure around your neck at collar level. Leave about two finger spaces for comfort.
Stand naturally, measure around the fullest part of the chest, keeping the tape under the arms and around the shoulder blades.
Measure around your natural waist, that is where the bend is at your side.
If you stand in front of a mirror and bend to the side the crease that forms indicates your natural waistline.
Hold one finger between your body and the tape while measuring your waist.