Body Fat Calculator — US Navy Method, Free, No Upload
Estimate your body fat percentage using the US Navy circumference method — one of the most accurate tape-measure techniques available. Enter height, waist, neck, and (for women) hip measurements. Metric and imperial supported. Everything runs in your browser.
How to use this tool
- Enter your age, sex, height, and weight.
- Add optional measurements (neck, waist, hips).
- See your estimated body fat percentage.
About Body Fat Calculator
The Body Fat Calculator estimates what percentage of your weight is fat using the US Navy circumference method, a tape-measure technique that needs no calipers, scales, or scans. You choose your sex and unit system, then enter a few body measurements: height, the circumference of your waist, and your neck. For women a hip measurement is also required, because the female formula accounts for fat distribution differently than the male one. Measurements can be entered in centimetres or inches, and inches are converted to centimetres before the calculation runs.
The method works by relating the sizes of fat-storing and non-fat-storing areas through logarithmic regression equations developed by the US Navy. For men it uses waist minus neck and height; for women it uses waist plus hip minus neck and height. The formula produces a body fat percentage that is rounded to one decimal place and then mapped to a descriptive band. For men the bands run from essential fat, athletes, and fitness to average and obese; for women the same labels apply at higher percentages, reflecting the greater essential fat that female physiology requires.
Accurate measuring matters more than the formula. Use a flexible tape held snug but not compressing the skin, measure the waist at the navel, the neck just below the larynx, and the hips at the widest point, and take each reading on bare skin while relaxed rather than sucking in. Because the method depends on circumferences rather than direct fat measurement, it can be off for very lean, very muscular, or unusually proportioned bodies, and it rejects results that fall outside a plausible range so you can recheck your numbers. For tracking change over time, what counts most is measuring the same way each time.
This is informational, not medical advice or a clinical assessment. The calculation happens entirely in your browser, so your measurements are never uploaded. Compared with bathroom devices, the Navy method is a sensible no-cost option, but for a precise reading consider DEXA, hydrostatic weighing, or air-displacement testing, and discuss any health decisions with a qualified professional.
Frequently Asked Questions
- What method does this calculator use?
- It uses the US Navy circumference (tape-measure) method. This applies logarithmic regression equations to body measurements rather than measuring fat directly, which is why it needs no special equipment beyond a flexible tape and a way to record your height.
- What measurements do I need?
- Everyone enters height, waist circumference, and neck circumference. Women additionally enter hip circumference, because the female equation uses waist plus hip minus neck while the male equation uses waist minus neck. The tool requires the hip value for women and will not calculate without it.
- Can I use inches instead of centimetres?
- Yes. Select the imperial unit and enter your measurements in inches; the tool multiplies them by 2.54 to convert to centimetres before running the formula. Metric users enter values directly in centimetres.
- How accurate is the Navy method?
- For most people it lands within a few percentage points of more advanced methods, which is good for a free tape measurement. It is less reliable for very lean, very muscular, or unusually proportioned bodies because it infers fat from circumferences. If your inputs produce an implausible value, the tool flags it so you can re-measure.
- How should I take the measurements?
- Use a flexible tape on bare skin, snug but not tight. Measure the waist at the navel, the neck just below the larynx, and the hips at the widest point. Stay relaxed and breathe normally rather than tensing or holding your stomach in, and try to measure at the same time of day for consistent tracking.
- What do the categories mean?
- The result is labelled essential fat, athletes, fitness, average, or obese. Women's bands sit at higher percentages than men's because female bodies require more essential fat for normal physiological function. The labels are general reference ranges, not health diagnoses.
- Is a body scan more accurate?
- Yes. DEXA scans, hydrostatic weighing, and air-displacement (Bod Pod) testing are more precise but require equipment and cost money. The Navy method is a practical free alternative, and measuring yourself the same way each time gives a useful trend even if the absolute number is approximate.
- Is my data private?
- Yes. All processing runs locally in your browser and nothing is sent to a server, so your measurements stay on your device.
Embed this tool on your site
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