Body Fat Calculator (US Navy Method)
Estimate body-fat percentage from neck, waist, hip, and height using the US Navy circumference method (Hodgdon-Beckett, 1984), with metric and imperial units.
Estimated results
These are general estimates, not medical advice.
How this calculator works
How the US Navy method works
The US Navy method estimates body-fat percentage from tape-measure circumferences and height, using the equations developed by Hodgdon and Beckett at the Naval Health Research Center in 1984. For men it uses neck, waist, and height; for women it adds the hip. The measurements feed a logarithmic regression that was fitted against body density from hydrostatic weighing. The equation is sex-binary by design, applying a separate formula for men and women rather than making any statement about identity.
The equations
With all measurements in centimetres and logarithms in base 10, the formulas are: for men, body fat = 495 / (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450; for women, body fat = 495 / (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450. Imperial inches are converted to centimetres before the calculation, so the result is identical in either unit.
How to measure correctly
Accurate tape measurements matter more than anything else here. The neck is measured just below the larynx with the tape sloping slightly downward to the front. The waist is measured horizontally at the level of the navel for men and at the narrowest point for women. The hip, used only for women, is measured at the widest point of the buttocks. The tape should be snug but not compress the skin, and measurements are taken on bare skin after a normal breath out.
Worked example
A man who is 180 cm tall with a 90 cm waist and a 40 cm neck has an estimated body fat of about 18.4%: 495 / (1.0324 − 0.19077 × log10(50) + 0.15456 × log10(180)) − 450. A woman who is 165 cm tall with a 75 cm waist, 95 cm hip, and 34 cm neck has an estimated body fat of about 26.4%. To turn an estimate like this into daily calorie targets, the TDEE calculator pairs naturally with this tool.
Frequently asked questions
- How accurate is the US Navy body fat calculator?
- It is a reasonable estimate, not a measurement. The circumference method has been reported to fall within roughly ±3–4% of hydrostatic weighing on average, though individual error can be larger and accuracy declines at the extremes of body fat. Careful, consistent tape placement is the biggest factor in getting a usable number, so tracking the trend over weeks is more reliable than any single reading.
- Where do I measure my neck, waist, and hips?
- The neck is measured just below the larynx, with the tape angled slightly downward at the front. The waist is measured horizontally at the navel for men and at the narrowest point of the torso for women. The hip, needed only for the women's equation, is measured at the widest part of the buttocks. The tape should sit snug against bare skin without compressing it, taken after a normal exhale.
- Why does the calculator ask for hips only for women?
- The Hodgdon-Beckett equations are two separate sex-specific formulas. The women's equation adds the hip circumference because it improved the fit against measured body density for women in the original Navy data, while the men's equation uses only neck, waist, and height. The split is a feature of how the equations were derived, not a statement about identity.
- Is body fat percentage better than BMI?
- They answer different questions. BMI uses only height and weight and cannot separate muscle from fat, so a muscular person can read as overweight. A body-fat estimate tries to capture composition directly, which can be more informative, but the circumference method is still an estimate with its own error. Using both, alongside measures like waist circumference, gives a fuller picture than either alone. The TDEE calculator on this site reports BMI for comparison.
References
- Prediction of percent body fat for U.S. Navy men and women from body circumferences and height (Report No. 84-11 / 84-29) — Hodgdon JA, Beckett MB, Naval Health Research Center (1984). Accessed 2026-05-27.
- The U.S. Navy body fat estimation formula — Medicine LibreTexts (Physiology Labs at Home, Anthropometrics). Accessed 2026-05-27.