Body Fat Percentage Calculator
Estimate your body fat percentage from tape measurements using the US Navy circumference method.
Category ranges (men)
| Essential fat | 2–5% |
| Athletic | 6–13% |
| Fit | 14–17% |
| Average | 18–24% |
| Obese | 25%+ |
Tape-measure estimates can differ from lab methods by 3–4 percentage points. This is not medical advice.
How it works
- Select your sex and choose metric or imperial units.
- Measure your height, neck and waist with a tape measure — women also measure hips at the widest point.
- Read your body fat percentage, category and lean mass estimate, which update as you type.
Frequently asked questions
- How does the US Navy body fat method work?
- It estimates body density from circumference measurements — neck and waist for men, plus hips for women — combined with height. A logarithmic regression formula developed by the Naval Health Research Center converts these into a body fat percentage. It was designed for quick screening of large groups without lab equipment.
- How accurate is the Navy tape measure method?
- Studies put it within 3-4 percentage points of DEXA scans for most people, which is respectable for a method that needs only a tape measure. It tends to overestimate body fat in very lean, muscular people and underestimate it at higher body fat levels. Measuring at the same time of day and keeping the tape level improves consistency more than anything else.
- Where exactly do I measure my waist and neck?
- Measure the neck just below the larynx with the tape sloping slightly downward at the front. Men measure the waist at the navel; women measure at the narrowest point of the abdomen. Keep the tape snug against the skin but not compressing it, and measure after a normal exhale.
- What is a healthy body fat percentage?
- Widely used fitness categories put the average range at roughly 18-24% for men and 25-31% for women, with fitness ranges just below that. Essential fat — the minimum needed for normal physiology — is about 2-5% for men and 10-13% for women. Healthy targets vary with age, sport and genetics, so treat the categories as orientation rather than a verdict.
- Is my measurement data stored or uploaded anywhere?
- No. The entire calculation runs in JavaScript inside your browser, and nothing you enter is sent to a server or saved anywhere. You can disconnect from the internet after the page loads and the calculator keeps working.
About this tool
This calculator estimates body fat percentage with the US Navy circumference method, a formula the Naval Health Research Center developed so body composition could be screened with nothing more than a tape measure. You enter height, neck and waist measurements — women add a hip measurement — and the result updates instantly as you type. Optionally add your weight to see an estimated split between fat mass and lean mass in kilograms or pounds.
Under the hood the tool applies the published Navy regression equations, which relate the logarithms of your circumference values and height to body density and then to fat percentage. Everything happens client-side in your browser: no measurements are transmitted, logged or stored. The result is classified into standard fitness categories — essential fat, athletic, fit, average and obese — using the commonly cited American Council on Exercise ranges, which differ for men and women because women naturally carry more essential fat.
The tape method is most useful for tracking change over time. A single reading can be off by a few percentage points compared with a DEXA scan, but if you measure the same sites, at the same time of day, with the same tape tension, the trend line is meaningful. Many people take measurements weekly alongside a scale weight; body fat trending down while weight holds steady usually indicates fat loss with muscle retention, something the scale alone cannot show.
For the best reading, measure in the morning before eating, stand relaxed without sucking in your stomach, and take each circumference two or three times, averaging the results. Use a flexible, non-stretch tape and keep it parallel to the floor. Round to the nearest half centimetre or quarter inch — false precision in the inputs does not make the estimate more accurate.