Body Fat Calculator
Enter your measurements with a tape measure to get an estimated body fat percentage, fat and lean mass, and where you fall on the ACE scale.
US Navy circumference method; typically within 3–4 percentage points of a DEXA scan. Not a medical diagnosis.
About this tool
Body fat percentage says more about fitness than weight or BMI, because muscle is heavy. The US Navy method estimates it from circumferences: neck and waist for men, plus hips for women, combined with height in a logarithmic formula validated against underwater weighing. It is the same calculation the military uses for fitness standards.
Measure the waist at the navel, the neck just below the larynx, hips at the widest point, all with the tape snug but not tight. Take the average of two or three readings. Categories follow the American Council on Exercise: essential fat, athletes, fitness, average, obese.
Frequently asked questions
- How accurate is it?
- Usually within 3–4 percentage points of a DEXA scan when measurements are taken carefully. Tracking changes over time is more reliable than a single reading.
- Why do women need the hip measurement?
- Women store proportionally more fat around the hips, so the formula needs that circumference to be accurate.
- What is essential fat?
- The minimum needed for basic physiological functions: about 2–5% for men and 10–13% for women.