Body Fat Calculator
Get a body-fat-percentage estimate from a few tape-measure inputs using the U.S. Navy circumference formula — no scale or calipers required.
Get a body-fat-percentage estimate from a few tape-measure inputs using the U.S. Navy circumference formula — no scale or calipers required.
How to use Body Fat Calculator
- 1
Pick gender and unit system (cm or in) — the Navy formula uses different equations for men and women.
- 2
Measure neck circumference just below the larynx with the tape level, and waist at the navel for men or at the narrowest point for women.
- 3
Women add a hip measurement — the largest horizontal circumference around the buttocks.
- 4
Type values in and read the body-fat estimate plus its category: essential, athletic, fitness, average, or obese.
Real examples of Body Fat Calculator in action
Inputs in cm
~17.5% body fat — Fitness category
Inputs in cm
~24% body fat — Fitness category
Who is Body Fat Calculator for?
Home-gym athletes tracking recomposition without buying expensive equipment
Coaches and personal trainers needing a quick estimate during consultations
People dieting who want a metric better than bathroom-scale weight
Recreational runners and lifters periodizing body composition around a season
Anyone whose smart-scale readings vary wildly day to day
Why use Body Fat Calculator?
- Uses the U.S. Navy circumference formula — peer-reviewed and within ~3% of DEXA-scan body-fat results for most people.
- Needs only a soft tape measure, not a scale, calipers, or bioimpedance device.
- Gender-specific equations (men use neck/waist; women use neck/waist/hip) for accurate results across body types.
- Categorizes the result with the ACE fitness reference ranges so you know whether you're in the athletic or average band.
Common use cases
- Track recomposition progress over a 12-week cut without buying a smart scale.
- Sanity-check the body-fat reading from a bioimpedance scale, which can be wildly inaccurate.
- Set a realistic body-fat target for an upcoming photo shoot or sport season.
- Coach clients who train at home and have only a tape measure available.
How Body Fat Calculator keeps your data private
Body fat percentage is sensitive personal data — many fitness apps treat it as a profile attribute and share it with ad networks. We never see your inputs or result. The calculation is plain JavaScript that runs once per keystroke, with no analytics on the values themselves.
How Body Fat Calculator compares to alternatives
Honest comparison to other popular options — pick the right tool for the job.
| Tool | Main limitation |
|---|---|
| Smart bioimpedance scale | Notoriously variable; readings swing 4-6% with hydration alone |
| DEXA scan | Most accurate but costs $50-150 per scan and requires a clinic visit |
| Skinfold calipers | Accuracy depends heavily on tester technique and is hard to self-administer |
| Body Fat Calculator | Free, runs in your browser, no sign-up, no watermarks, no file-size limits beyond your device memory. |
Limitations & things to know
- Validated on adults — not appropriate for children or teens
- Edge cases (very muscular athletes, post-surgery body shapes) may produce less accurate readings
- Single-point estimate — for trend tracking, log results weekly under consistent conditions
About Body Fat Calculator
Bioimpedance scales lie. They estimate body fat by sending a tiny current through your feet and measuring resistance, but the result swings wildly with hydration, recent meals, and time of day. The U.S. Navy circumference method, originally developed to screen recruits, uses a different and more stable approach: simple body circumference measurements plugged into a logarithmic regression. Xevon Tools' Body Fat Calculator implements that formula faithfully — separate equations for men (waist minus neck divided by height) and women (waist plus hip minus neck divided by height) — and reports both the percentage and the standard ACE fitness category. The result is a body-fat estimate within a few percentage points of a DEXA scan for the average adult, with none of the day-to-day noise of a smart scale. Best of all, it requires no equipment more sophisticated than a $5 cloth tape measure. Run the math weekly under the same conditions (morning, before food, after the bathroom), and the trend line reveals real recomposition progress that a bathroom scale's bouncing weight alone hides. Every input is processed locally; we don't see your measurements, store your weight history, or sell your fitness data to insurance brokers. That's a meaningful difference compared to most free body-fat calculators, which treat your inputs as ad-targeting fuel.
Frequently asked questions
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