Body Fat Calculator

Estimate body fat percentage from tape measurements (US Navy method).

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Health information notice

This tool gives a general estimate only. It is not a diagnosis, a medical device or a substitute for professional advice. Simple formulas cannot account for your individual circumstances — the assumptions and limitations listed below describe the groups this model is not suitable for.

If the result concerns you, or you are making any health decision based on it, speak to a GP, midwife, pharmacist or other qualified health professional. The health figures you enter are used only to calculate your result and are not intentionally retained — see our privacy policy.

About this calculator

The US Navy circumference method estimates body fat percentage from a tape measure — height, neck and waist (plus hips for women). It's not a lab measurement, but it tracks change well and adds the composition context that BMI lacks: two people with identical BMI can differ enormously in body fat.

The formula

Men: 495 ÷ (1.0324 − 0.19077·log₁₀(waist−neck) + 0.15456·log₁₀(height)) − 450 Women: 495 ÷ (1.29579 − 0.35004·log₁₀(waist+hip−neck) + 0.22100·log₁₀(height)) − 450

Worked example

Male, 175cm, neck 38cm, waist 88cm: estimated body fat ≈ 19.8% — inside the typical 10–20% healthy range for men.

Common mistakes

Pulling the tape tight — measure snug but not compressing.
Measuring the waist at the trouser line instead of the navel.
Comparing measurements taken at different times of day.

Frequently asked questions

Typically within ±3–4% of DEXA for most physiques — excellent for tracking direction of change, less so for absolute precision.

Roughly 10–20% for men and 18–28% for women, rising slightly with age. Essential fat minimums are ~3% (men) and ~12% (women).

Female fat distribution differs; the hip measurement corrects the estimate for it.

Assumptions & limitations

US Navy formula, metric inputs; not validated for pregnancy or bodybuilder-level physiques.

Sources & verification

Hodgdon, J.A. & Beckett, M.B. (1984) — “Prediction of percent body fat for U.S. Navy men/women from body circumferences and height”, Naval Health Research Center reports 84-11 and 84-29 — the “US Navy method” this calculator implements

All sources last accessed 24 July 2026.

Formula last verified: 24 July 2026

Maintained by: Steve Davis, Founder & Editor — see our editorial standards

Spotted an error or an out-of-date figure? Report it — corrections are prioritised over all other work (see our corrections policy).