What Is Body Fat Percentage?

Body fat percentage is the share of your body weight that is fat: fat mass divided by weight. The rest is lean body mass: muscle, bone, water and organs. It is estimated from tape measurements, skinfolds, bioelectrical impedance or a DEXA scan. Two people of the same weight can have very different body fat. This page is not medical advice.

Where it appears in the formulas

The body fat calculator finds it with the U.S. Navy method: first the body density from the neck, waist and height (and the hip for women), then body fat = 495 / density − 450. After that, fat mass = weight × body fat and lean mass = weight − fat mass. Example: 80 kg at 20.1% body fat is 16.1 kg of fat mass and 63.9 kg of lean mass.

The difference from BMI

BMI uses weight and height only; it cannot tell muscle from fat. A muscular person can have a high BMI and a low body fat percentage. Body fat is read with the ACE table: 18–24% for men and 25–31% for women is the average class; the limits for women are higher.