Measure according to body type. If belly is larger than hips: Measure at the same angle you wear your pants, from the small of your back to a point 3"- 4" below your navel. For men, this is your pant size. If waist is smaller than hips: Measure at waistline. Back-A-Line fits most men and many women, but not all.
Adds about 1.5" to body circumference if worn under clothing.