Body Fat Calculator (Navy Method)
This calculator estimates your body fat percentage using the U.S. Navy (Hodgdon-Beckett) method, a tape-measure formula the military uses for body-composition screening. It needs only a flexible tape: your waist, neck, and height for men, plus your hip for women. Because it captures where you carry size — not just total weight like BMI — it gives a more useful picture of body composition for most people. It is still an estimate: the equation was fitted to a population, so it can differ from a clinical measurement such as a DEXA scan by several percentage points. Use it to track trends over time rather than as an exact, diagnostic number.
Calculate
Default result: 15.5
Body Fat Calculator (Navy Method) · Result
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Body fat
male × 34 in × 16 in × 70 in × 40 in
This calculator provides an estimate for general information only and is not a medical diagnosis or professional advice. Body-composition and health-risk figures are approximations from population formulas and can differ meaningfully from clinical measurement. Do not use this result to diagnose, treat, or rule out any health condition — consult a qualified healthcare provider before acting on it.
Reviewed by the calculators.dev team · Last updated 2026-06-23
Formula reviewed against Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy men/women from body circumferences and height. Naval Health Research Center, 1984
How to calculate
Choose your sex and measure with a flexible tape, keeping it level and snug but not compressing the skin. Measure your waist at the navel while relaxed, your neck just below the larynx, and your height without shoes. Women also measure the hip at its widest point. Enter the values and the calculator applies the Navy equation. For a man with a 34-inch waist, 16-inch neck, and 70-inch height, the estimate is about 15.5%. Take each measurement twice and average them — small tape errors at these sites move the result the most.
Men: %BF = 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76. Women: %BF = 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387. Variables: waist, neck, hip, and height are circumferences/height in inches (the calculator accepts inches or centimetres and converts). The formulas are logarithmic regressions fitted to military personnel, so accuracy is best for typical builds and degrades at the extremes of body composition.
Example calculation
A man with a 34-inch waist, a 16-inch neck, and a height of 70 inches has a Navy body-fat estimate of 86.010 × log₁₀(34 − 16) − 70.041 × log₁₀(70) + 36.76 ≈ 15.5%. The men's formula uses only waist, neck, and height; the women's formula adds the hip measurement.
- bodyFatPercent
- 15.5%
Assumptions
- Measurement sites are exact and matter most: waist at the navel, neck below the larynx, and (women) hip at the widest point. Measuring elsewhere is the largest source of error.
- The equation is a population regression, not a direct measurement; it can differ from a DEXA or hydrostatic result by several percentage points.
- The men's and women's formulas are different — the women's equation requires a hip measurement and is never substituted with the men's.
Common mistakes
- Measuring the waist at the belt line or while holding the stomach in. Measure at the navel, relaxed — this is the single biggest source of error.
- Pulling the tape tight enough to compress the skin, which understates circumferences and skews the estimate.
- Treating the percentage as a clinical diagnosis. It is a screening estimate; a body-composition scan is needed for a precise figure.
Frequently asked questions
How accurate is the Navy body fat method?
For typical body types it is reasonably close to lab methods — usually within a few percentage points — and far better than BMI at distinguishing fat from muscle. It is still an estimate and works best when the tape measurements are taken at the correct sites.
Where exactly do I measure my waist and neck?
Measure the waist horizontally at the navel while relaxed, and the neck just below the larynx (Adam's apple), sloping slightly downward at the front. Women also measure the hip at its widest point. Correct sites are the most important factor in a good estimate.
Why does the women's formula need a hip measurement?
Women's body-fat distribution differs, so the Navy method uses a separate equation that includes the hip circumference. The men's formula uses only waist, neck, and height. The right formula is chosen automatically from the sex you select.
Is this the same as a body fat scale or DEXA scan?
No. This is a tape-measure estimate. Bioelectrical scales and DEXA scans measure body composition differently and can give different numbers. Use the Navy method to track your own trend over time rather than as an exact clinical value.