Body Fat Calculator
Estimate adult body-fat percentage from circumference measurements using a transparent U.S. military method in metric or US units.
Calculate your estimate
What this tool tells you
This calculator uses sex-specific circumference equations documented in U.S. military guidance. It estimates body-fat percentage indirectly from height and tape measurements; it does not measure fat tissue or diagnose health.
How the estimate works
All measurements are converted to inches before calculation. The male equation is 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76. The female equation is 163.205 × log10(waist + hips − neck) − 97.684 × log10(height) − 78.387. The logarithm is base 10. Metric entries are divided by 2.54, the unrounded converted values are used, and the final estimate is rounded to one decimal place.
How to measure for this calculator
- Use a flexible, non-stretch tape. Keep it level and snug without compressing the skin.
- Height: stand upright without shoes and measure vertical height.
- Neck: measure just below the larynx, avoiding the shoulder muscles; keep the tape gently in contact with the skin.
- Waist: for the male equation, measure level at the navel after a normal exhale. For the female equation, measure the natural waist at the narrowest point.
- Hips for the female equation: measure level around the widest part of the hips and buttocks.
- Repeat each circumference measurement consistently. If repeated values differ, recheck tape position before using the calculator.
Important limitations
Circumference equations are field estimates derived from particular populations. Tape placement, body shape, and ordinary measurement variation affect the result. Studies have found disagreement with DXA and poor sensitivity to some short-term composition changes. DXA, air-displacement plethysmography, skinfolds, and bioelectrical impedance use different assumptions and can also disagree. Do not treat this estimate as equivalent to DXA, a diagnosis, or a complete picture of health.
Frequently asked questions
Is this the same as a DXA scan?
No. It is a circumference-based prediction. DXA uses low-dose X-rays and a different body-composition model; the two results can differ.
Why does the female equation ask for hips?
The documented female equation uses waist plus hip circumference minus neck circumference. The male equation uses waist minus neck.
Should I use the result as a health diagnosis?
No. Body-fat estimates vary by method and population, and one number cannot diagnose health.
Why can repeated results change?
Small changes in tape location, tension, posture, or breathing can change circumference values and therefore the estimate.
Understand the estimate
Compare body-fat methods, learn why results change, and keep the number in context with BMI, weight, energy, and lean mass.