The Navy method
The US Navy estimates body fat from a few tape measurements and height, using equations published by Hodgdon and Beckett in 1984. It needs no special equipment and is usually within a few percentage points of lab methods when the measurements are taken carefully.
How to measure
- Neck: just below the Adam's apple, tape sloping slightly down to the front.
- Waist: men at the navel; women at the narrowest point. Relax, don't suck in.
- Hips (women): around the widest part of the buttocks.
- Measure twice and use the average.
Worked example
A man 5 ft 10 in tall with a 15 in neck and 34 in waist: 86.010 × log(34 − 15) − 70.041 × log(70) + 36.76 = 17.5% body fat, in the "fitness" range.
Categories (American Council on Exercise)
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletes | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Obese | 25%+ | 32%+ |
How this works
The page converts centimeters to inches if needed and applies the Navy equation for your sex: for men it uses the waist minus the neck, for women the waist plus hip minus the neck, each with height on a logarithmic scale. If you enter your weight, fat mass is weight times the body-fat percentage and lean mass is the rest. The category comes from the American Council on Exercise table.
Frequently asked
How accurate is the Navy body fat method?
Typically within 3–4 percentage points of DEXA or underwater weighing, if measured carefully.
Where do I measure my waist?
Men at the navel, women at the narrowest point between ribs and hips.
What is a healthy body fat percentage?
Roughly 14–24% for men and 21–31% for women fall in the fitness and average ranges.
Why do women measure hips?
The female equation includes hip circumference because women store more fat around the hips.
Sources
- U.S. Navy Physical Readiness Program — Guide 4: Body Composition Assessment (circumference method)
- American Council on Exercise — Percent body fat calculator and categories
- Wikipedia — Body fat percentage
Reviewed Oct 17, 2026 · test vectors fixtures/calculators/health/body-fat-calculator/