Body Fat Calculator
Estimate your body fat percentage using the U.S. Navy tape method — all you need is a tape measure.
Your results
What is the Navy body fat method?
This body fat calculator estimates your body fat percentage from tape measurements — height, neck and waist (plus hips for women) — using the method developed for the U.S. Navy. All you need is a soft tape measure, which makes it the most practical body fat test you can do at home.
How it works
The formulas were developed by Hodgdon and Beckett at the Naval Health Research Center in 1984 by regressing circumference measurements against hydrostatic (underwater) weighing — then the gold standard. They use log-transformed circumferences:
- Men: 495 / (1.0324 − 0.19077·log₁₀(waist − neck) + 0.15456·log₁₀(height)) − 450
- Women: 495 / (1.29579 − 0.35004·log₁₀(waist + hip − neck) + 0.221·log₁₀(height)) − 450
Validation studies put the accuracy at roughly ±3% versus laboratory methods for most people — comparable to consumer bioimpedance scales, with none of the hydration sensitivity.
How to measure correctly
- Waist: at the navel, relaxed — don't suck in
- Neck: just below the larynx, tape sloping slightly downward at the front
- Hips (women): at the widest point
- Same time of day, tape snug but not compressing skin, average of two readings
Frequently asked questions
What's a healthy body fat percentage?
The American Council on Exercise's categories: for men, athletes run 6–13%, fitness 14–17%, average 18–24%; for women, athletes 14–20%, fitness 21–24%, average 25–31%. Essential fat — the minimum for health — is about 3% for men and 12% for women.
Why does it differ from my smart scale?
Bioimpedance scales swing several percent with hydration, food and time of day. Neither method is lab-grade; both track trends well. Pick one, measure consistently, watch the direction.
References
- Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy men and women from body circumferences and height. Naval Health Research Center Reports 84-29 & 84-11. 1984.
- Babcock CJ, Kirby TE, et al. A comparison of military circumference equations to skinfold-based equations. Mil Med. 2006;171(1):60–63.
Related
These results are estimates for healthy adults and are not medical advice. Consult a health professional before making major changes to your diet or training.
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