How does the U.S. Navy body-fat formula work?

It estimates body density from tape-measured circumferences. For men: 495 / (1.0324 − 0.19077·log10(waist − neck) + 0.15456·log10(height)) − 450. For women: 495 / (1.29579 − 0.35004·log10(waist + hip − neck) + 0.22100·log10(height)) − 450, with all measurements in centimeters.

How accurate is the Navy circumference method?

It typically lands within about 3–4 percentage points of lab methods like DEXA for most people. Accuracy depends on consistent tape placement — measure at the same landmarks, relaxed, and take the average of two or three readings.

What is a healthy body-fat percentage?

Common ACE-style bands: for men, athletes 6–13%, fitness 14–17%, average 18–24%, and 25%+ classified as obese. For women, athletes 14–20%, fitness 21–24%, average 25–31%, and 32%+ classified as obese. Essential fat is roughly 2–5% for men and 10–13% for women.

Body-Fat % Calculator (U.S. Navy Method)

Your measurements

Sex

Units

Height

Weight

Used for the fat / lean mass breakdown.

Neck circumference

Just below the larynx, tape sloping slightly down in front.

Waist circumference

At the navel (men) or the narrowest point (women).

Estimated body fat

— %

—

Fat mass—

Lean mass—

Category bands (ACE-style): Men — essential 2–5%, athletes 6–13%, fitness 14–17%, average 18–24%, obese 25%+. Women — essential 10–13%, athletes 14–20%, fitness 21–24%, average 25–31%, obese 32%+.

How this works

Methodology reviewed July 2026

This tool estimates body-fat percentage with the U.S. Navy circumference method — a tape-measure formula that uses the log of your waist, neck (and hip, for women) against height. It's not as precise as a DEXA scan, but it's free, repeatable, and good at tracking change over time.

Formula

Men:   %BF = 495 / (1.0324 − 0.19077·log10(waist − neck) + 0.15456·log10(height)) − 450
Women: %BF = 495 / (1.29579 − 0.35004·log10(waist + hip − neck) + 0.22100·log10(height)) − 450
(circumferences and height in cm, base-10 logs)

Inputs

Sex · Height · Neck · Waist · Hip (women)

Outputs

Estimated body-fat % · Lean vs fat mass · Category rating

Assumptions

Measurements are taken snugly with a flexible tape at the standard landmarks.
The Navy equations were derived on general adult populations and assume typical fat distribution.

Limitations

Circumference methods can be off by several points versus DEXA, especially at the extremes.
Consistency matters more than absolute accuracy — measure the same way each time to track change.

Safety

Body-fat percentage is one signal among many and says nothing on its own about health.

This calculator is for educational purposes only and is not medical advice, diagnosis, or treatment. Results are estimates based on published formulas and population averages — your individual values may differ. Nothing here is calculated on a server: everything runs in your browser and no data is stored or sent anywhere. Always consult a qualified clinician before making health, medication, or training decisions.