Body Fat Calculator
Estimate body fat percentage from tape measurements using the US Navy circumference method.
Last updated · View algorithm, constants and default inputs (JSON)
About this calculator
This simplified U.S. Navy-style circumference equation estimates body-fat percentage from height, neck, waist and (for the female equation) hip measurements. Tape placement and individual body shape affect the result; it is not a direct measurement, diagnosis or official military assessment. Weight is used only to estimate fat and lean mass from the percentage.
Worked example
calculated with the default values below
Sex Male · Height 178 cm · Neck circumference 38 cm · Waist circumference 85 cm · Hip circumference (women) 95 cm · Body weight 80 kg Body fat 10.1 % · Fat mass 8.1 kg · Lean mass 71.9 kg
General background references
Disclaimer
These calculators are for general information only and are not a medical device, a diagnosis or a treatment plan. Reference ranges describe populations, not individuals, and do not account for pregnancy, medication, disability or athletic training. Discuss your own situation with a qualified healthcare professional.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
BF = 495/(1.29579 − 0.35004·log10(W+Hp−N) + 0.22100·log10(H)) − 450 ♀; 495/(1.0324 − 0.19077·log10(W−N) + 0.15456·log10(H)) − 450 ♂
- H
- Height (in)
- N
- Neck circumference (in)
- W
- Waist circumference (in)
- Hp
- Hip circumference, female only (in)
- BF
- Body fat percentage
US Navy circumference method; centimetres are converted to inches (÷2.54); BF is clamped to 2–70%; fat mass = weight × BF/100.
Frequently asked questions
How precise is this tape-measure estimate?
The tool estimates body-fat percentage from height, neck and waist measurements, plus hip measurement for the female setting. It does not clamp a valid result to a preset percentage range; measurements that produce an invalid estimate show an error. This is still an equation-based estimate, not a direct measurement, scan result or diagnosis. Measurement placement and body shape can affect it.
Where should I measure my waist for this estimate?
Use the measurement locations specified by the formula instructions and keep them consistent when comparing results. The calculator does not verify tape placement, so changing the location can change the estimate.