Estimate adult body-fat percentage with a sex-specific U.S. Navy circumference equation, explicit measurement guidance, unit conversion, and non-diagnostic limitations.
Choose your path
Estimate adult body-fat percentage from clearly specified circumference measurements while exposing method limits, measurement technique, and non-diagnostic interpretation.
Repeat a consistent circumference-based estimate over time.
Select the applicable equation, enter correctly located measurements, and record the result plus method.
Can reproduce the measurement technique and treats trend consistency as more meaningful than false precision.
Receive the same estimate after unit conversion.
Enter inches or switch from centimetres, then compare preserved physical measurements and result.
Metric and imperial paths agree within rounding tolerance.
Avoid treating a circumference equation as diagnosis or a universal category.
Read population/method limitations, verify inputs, and review alternative professional measurement options.
Recognizes the estimate can be unsuitable individually and seeks qualified assessment when consequential.
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The male equation uses height, abdomen circumference at navel level, and neck circumference. This implementation uses the centimetre form of the body-density equation and rejects an abdomen measurement that is not greater than the neck measurement.
Men: BF% = 495 ÷ (1.0324 − 0.19077×log10(waist−neck) + 0.15456×log10(height)) − 450The female equation uses height, natural waist, neck, and widest-hip circumferences. Hip is required, and waist plus hip must be greater than neck. The sex selection chooses the published equation; it is not a statement about gender identity.
Women: BF% = 495 ÷ (1.29579 − 0.35004×log10(waist+hip−neck) + 0.22100×log10(height)) − 450This is a circumference estimate, not a direct tissue measurement, diagnosis, health category, or recommended target. Fat and lean mass are derived arithmetically from entered weight. The calculator never silently substitutes a BMI-based formula when circumference inputs are invalid.
Estimated fat mass = entered weight × estimated BF%; estimated lean mass = entered weight − estimated fat massUpdated: August 2026
An adult records measurements at the same sites and under similar conditions so later results can be compared on the same method—not treated as clinical truth.
→ Estimated body fat: 16.1%; derived fat mass: 12.9 kg; derived lean mass: 67.1 kg
The female equation requires the hip measurement and reports an explicit error rather than changing methods when it is missing.
→ Estimated body fat: 27.4%; derived fat mass: 17.8 kg; derived lean mass: 47.2 kg
Switching 180 cm, 85 cm, 38 cm, and 80 kg to imperial units preserves the physical measurements with sufficient decimal precision, so the estimate remains the same within display rounding.
Use a non-stretch tape and the sites specified for the selected equation. Keep the tape level and use similar conditions each time; small placement differences can materially change a circumference result.
Circumference equations can differ from criterion methods and may be less suitable for some individuals. Use the estimate for consistent general tracking and seek qualified assessment when a decision is consequential.
The male equation requires abdomen greater than neck; the female equation requires a positive hip and waist plus hip greater than neck. The calculator blocks invalid sets instead of falling back to BMI.
Use a transparent U.S. Navy circumference equation in metric or imperial units. The tool preserves unit-conversion precision, explains how to measure, and separates a repeatable estimate from diagnosis or target-setting.