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Body composition compares the proportion of fat mass to lean tissue in your body. Knowing this ratio, along with the body-mass index, helps you gauge health risks more accurately than weight alone. Fat percentage reflects stored energy and hormonal function, while lean mass represents muscle, bone, water and organs within total body weight.
Using the standard U.S. Navy circumference equations, this calculator estimates body-fat percentage from neck, waist, and—when relevant—hip measurements, adjusts for either metric or imperial units, and derives BMI plus absolute lean and fat mass. Results update instantly, display coloured gauges, composition charts, numeric tables, and highlight healthy ranges for your sex.
Track progress during weight-loss or strength programmes by recording circumference data weekly; interpret subtle shifts in lean mass rather than chasing scale numbers alone. Measurements must be taken snugly but not compressing the skin, preferably at the same time of day for consistency. This calculator offers informational estimates, not medical advice.
The tool employs the U.S. Navy circumference method, which models logarithmic relationships between girth differences and adipose tissue, and the conventional BMI equation. A lightweight reactive engine performs every calculation locally, while a client-side charting layer visualises the results.
| Symbol | Variable | Units |
|---|---|---|
| H | Standing height | cm / in |
| W | Body weight | kg / lb |
| N | Neck circumference | cm / in |
| Wa | Waist circumference | cm / in |
| Hip | Hip circumference (female) | cm / in |
| Category | Range % |
|---|---|
| Essential | 2 – 5 |
| Athlete | 6 – 13 |
| Fitness | 14 – 17 |
| Average | 18 – 24 |
| Obese | 25 + |
| Category | Range |
|---|---|
| Underweight | < 18.5 |
| Normal | 18.5 – 24.9 |
| Overweight | 25 – 29.9 |
| Obese | ≥ 30 |
Male body-fat equation
Example: H = 170 cm, Wa = 80 cm, N = 38 cm ⇒ BF ≈ 17.4 %
BMI and Lean-Mass
Using W = 70 kg and BF = 17.4 % ⇒ BMI ≈ 24.2, Lean-Mass ≈ 57.8 kg.
All maths run in microseconds inside the browser; no server calls occur. The debounce window limits recalculation to 25 fps, ensuring smooth typing even on low-power devices.
The workflow mirrors a tape-measure session at home. Follow the ordered steps once, then repeat the measurement routine periodically to monitor trends.
The U.S. Navy method balances simplicity and reliability, requiring only a tape measure while still reflecting regional fat distribution that weight-only metrics miss.
Stand relaxed. Measure neck just below the larynx, waist at the narrowest torso point, and hip (for females) at the fullest buttock area. Keep the tape level and parallel to the floor.
Typical error is ±3 – 4 % compared with DXA scans. Consistency of tape placement and posture impacts repeatability more than the formula itself.
No. All calculations take place locally in your browser; values disappear when you refresh or close the page.
The equations were validated on adults. Consult a paediatric health professional before interpreting results for anyone under 18 years of age.