A male reference case
A 30-year-old man, 178 cm tall, 80 kg, with a 38 cm neck and 85 cm waist, has an estimated body fat of about 16.4%.
Body fat percentage calculator
This is an estimate for information only. It is not a medical or clinical measurement and does not replace a body composition scan or advice from a healthcare professional.
Result
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How it works
The formula is a regression fit to body-density measurements taken alongside the same tape measurements in the original Navy study, separately calibrated for men and women. It tends to be more accurate than BMI alone because it captures where weight is distributed, not just total weight relative to height.
The BMI-based estimate shown alongside it uses only BMI, age and sex — a much rougher method included here only for comparison, since BMI cannot distinguish muscle from fat.
Formulas used
US Navy method (men)
%BF = 495 / (1.0324 − 0.19077×log₁₀(waist−neck) + 0.15456×log₁₀(height)) − 450
US Navy method (women)
%BF = 495 / (1.29579 − 0.35004×log₁₀(waist+hip−neck) + 0.221×log₁₀(height)) − 450
Worked examples
A female reference case
A 30-year-old woman, 165 cm tall, 65 kg, with a 34 cm neck, 75 cm waist and 95 cm hip, has an estimated body fat of about 26.4%.
Assumptions and limits
- Measurements are taken with a flexible tape, snug against the skin, at the described landmarks.
- The formula was validated on adult populations and may be less accurate for people far outside a typical body composition.
Frequently asked questions
How accurate is the US Navy method?
Studies generally find it within a few percentage points of DEXA (a body scan considered a gold standard) for most people, though accuracy drops at the extremes of leanness or body size.
Why does the formula need a hip measurement for women but not men?
Because typical fat distribution differs by sex — the original Navy regression found hip circumference added predictive value for women but not for men.
Where exactly do I measure?
Neck: just below the larynx. Waist: at the narrowest point, or at the navel if there is no narrowing. Hip: at the widest point around the buttocks. Measure snug but not compressed, without holding your breath.
Why do the two methods disagree?
BMI cannot tell muscle from fat, so the BMI-based estimate can be noticeably off for very muscular or very lean people — the tape-measure method is generally the more reliable of the two.
Updated
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