Body-fat calculator
The US Navy method estimates body fat from three tape measurements — no calipers, no lab, no scan appointment. Take the measurements as described under each field and you get a number worth tracking.
Tape measurements
Estimated body fat
Tape estimates run ±3–4 points vs a DEXA scan. Measure the same way at the same time of day — the trend matters more than any single number. Set your calories next →
These are estimates, not medical advice — see the medical disclaimer.
How the formula works
Developed at the Naval Health Research Center, the method predicts body density from circumference measurements, then converts it to a fat percentage. For men it uses waist minus neck against height; for women, waist plus hips minus neck. The logic: waist and hip girth grow with fat mass, neck girth mostly with lean mass, so the difference carries real signal about composition.
It is the same math the US military uses for body-composition standards — chosen exactly because it needs nothing but a tape measure and gives repeatable results.
Measuring sites
| Site | How to measure |
|---|---|
| Neck | Just below the Adam's apple, tape sloping slightly down at the front. Snug, not tight. |
| Waist (men) | At the navel, standing relaxed — no sucking in, no pushing out. |
| Waist (women) | At the narrowest point of the torso, standing relaxed. |
| Hips (women) | Around the widest point of the hips, feet together. |
Honest caveats
Expect ±3–4 percentage points versus a DEXA scan, and day-to-day noise from water, sodium, and carbs. That makes any single reading a rough estimate — but a consistent monthly measurement is a genuinely useful trend line. If BMI has been calling you overweight, this number tells you whether that is fat or muscle — compare it with your BMI, then set your calories with the TDEE calculator.
Common questions
How accurate is the Navy tape method?+−
Within about 3–4 percentage points of a DEXA scan for most people. That sounds loose, but measured consistently it tracks change well — and the trend is what training decisions actually run on.
When should I measure?+−
Morning, before food and water, after using the bathroom. Same tape, same spots, same posture every time. Changing the conditions changes the number more than your body does week to week.
Why does the female formula include hips?+−
Women store proportionally more fat around the hips, so the formula adds hip girth to capture it. Skipping the measurement or taking it in the wrong spot skews the estimate badly.
Is a lower body-fat percentage always better?+−
No. Essential fat sits around 2–5% for men and 10–13% for women, and living near those floors wrecks hormones, recovery, and performance. Most athletes compete and feel best well above them.
Change the number with a plan
Body composition follows training and food, in that order of difficulty. The 12-week program handles the training side for your sport.