Estimate your body fat percentage with a tape measure. This free body fat calculator uses the US Navy method to give your body fat %, a category, and your fat and lean mass – a quick estimate, not a target.
Measure relaxed, in a straight line: waist at the navel, neck below the larynx, hip at the widest point. The US Navy method estimates body fat from these.
An estimate – circumference methods have a margin of error and can’t replace tools like DEXA. Healthy ranges vary by individual; use this as a rough guide, not a target.
How the Body Fat Calculator Works
This tool estimates your body fat percentage from a few tape-measure readings, using the well-known US Navy circumference method. Rather than scanning your body, it plugs your measurements into a logarithmic formula that was originally developed to estimate body composition without lab equipment.
Formula: For men, Body Fat % = 495 ÷ (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450. For women, Body Fat % = 495 ÷ (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450. All measurements are used in centimeters (inches are converted × 2.54 automatically). If weight is provided: Fat mass = weight × Body Fat % ÷ 100, and Lean mass = weight − Fat mass.
- Sex — Male or female, since each uses a different Navy formula and hip is only required for female
- Height — measured standing straight, in cm or inches
- Neck — circumference measured just below the larynx
- Waist — circumference measured at the navel
- Hip (women) — circumference at the widest point; required only when Female is selected
- Weight (optional) — used only to also calculate fat mass and lean mass
Example Scenarios
| Sex | Height | Neck | Waist | Hip | Weight | Estimated Body Fat |
|---|---|---|---|---|---|---|
| Male | 180 cm | 38 cm | 85 cm | – | 80 kg | 16.1% (Fitness) |
| Male | 178 cm | 37 cm | 80 cm | – | 75 kg | 13.2% (Athletic) |
| Male | 175 cm | 40 cm | 100 cm | – | 95 kg | 26.0% (Above average) |
| Female | 165 cm | 32 cm | 70 cm | 95 cm | 60 kg | 24.9% (Fitness) |
| Female | 160 cm | 30 cm | 90 cm | 105 cm | 70 kg | 41.7% (Above average) |
How to Take Measurements for the Body Fat Calculator
The US Navy formula relies on a few tape readings, so a body fat calculator built on it is only as good as your measuring. Small errors at the neck or waist can shift the result noticeably.
- Waist: men usually measure horizontally at the navel, women at the narrowest point of the waist.
- Neck: measure just below the larynx, with the tape sloping slightly down toward the front.
- Hips (women): measure around the widest part of the buttocks.
- Keep the tape flat and snug; do not suck in.
Measure in the morning before eating, take each reading two or three times and use the average. Enter the same units throughout the body fat calculator.
Tape methods estimate fat rather than measure it directly, so a body fat calculator reading may differ from a DEXA scan or smart scale. Track the trend: repeat the body fat calculator monthly under the same conditions. The body fat percentage article on Wikipedia compares measurement methods and typical ranges. If your body fat calculator result worries you, a doctor can put it in context with other health checks.
Body Fat Calculator FAQ
How accurate is the US Navy body fat method compared to methods like DEXA?
It’s a reasonable field estimate for many people, but circumference measurements have a margin of error and can be affected by where exactly you measure. DEXA scans, hydrostatic weighing, and other lab methods are generally more precise. Use this as a general trend-tracking tool, not a diagnostic result.Why does the calculator ask for a hip measurement only for women?
The US Navy formula for women includes hip circumference alongside waist and neck, while the men’s formula uses only waist and neck. This reflects how body fat tends to distribute differently by sex, so the hip field only appears — and is required — when Female is selected.What counts as a healthy body fat percentage?
Ranges vary by individual, age, and goals, so there’s no single “correct” number. The categories shown here (Essential, Athletic, Fitness, Average, Above average) are common reference bands, not personal targets — a doctor or dietitian can help interpret your result if you have specific health concerns.Can I use inches instead of centimeters?
Yes. Switch the Units toggle to inches and enter your measurements as usual; the calculator automatically converts them to centimeters (multiplying by 2.54) before applying the formula, so results stay consistent either way.Do I need to enter my weight to get a body fat percentage?
No — the body fat percentage itself only needs height, neck, and waist (plus hip for women). Weight is optional and is only used to additionally calculate your estimated fat mass and lean mass.Why might my result change if I measure again later the same day?
Circumference measurements can shift slightly with hydration, food intake, posture, and exactly where the tape sits. Measuring relaxed, in a straight line, at a consistent time of day gives more comparable results over time than a single one-off reading.Related Calculators
Body fat percentage pairs well with other body-composition numbers: try the lean body mass calculator to see your fat-free weight from a different angle, the waist-to-hip ratio calculator to check how your fat is distributed, or the muscle mass calculator to estimate how much of your weight is muscle.