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Body-fat calculator — the US Navy method.
Your body-fat percentage is how much of your weight is fat versus lean mass. This calculator uses the US Navy circumference method — the log-based Hodgdon-Beckett equations from height, neck, and waist (plus hip for women) — to estimate body fat and lean mass in metric or imperial. No calipers, no signup, results live.
Body-fat categories.
Ranges differ by sex — women carry more essential fat. The table below matches the sex you selected in the tool.
| Category | Body fat | Look |
|---|---|---|
| Essential fat | 2 – 5% | The minimum for organ function |
| Athletes | 6 – 13% | Visible abs, competitive condition |
| Fitness | 14 – 17% | Lean and defined |
| Average | 18 – 24% | Typical healthy range |
| Obese | 25%+ | Elevated health risk |
| Category | Body fat | Look |
|---|---|---|
| Essential fat | 10 – 13% | The minimum for hormonal health |
| Athletes | 14 – 20% | Competitive condition |
| Fitness | 21 – 24% | Lean and defined |
| Average | 25 – 31% | Typical healthy range |
| Obese | 32%+ | Elevated health risk |
Category ranges follow the American Council on Exercise. The Navy estimate is accurate to about ±3–4 percentage points versus a DEXA scan and assumes a typical fat-distribution pattern, so very lean or very heavy bodies can read off by more. It's best for tracking change, not a single exact truth.
The US Navy formula, explained.
The real log-based equations, developed by Hodgdon and Beckett at the Naval Health Research Center in 1984. Measurements in centimetres.
495 ÷ (1.0324 − 0.19077 · log₁₀(waist − neck) + 0.15456 · log₁₀(height)) − 450 Only neck and waist are needed for men, because male fat sits mostly around the midsection.
495 ÷ (1.29579 − 0.35004 · log₁₀(waist + hip − neck) + 0.22100 · log₁₀(height)) − 450 Hip circumference is added for women to capture their different fat distribution.
lean = weight × (1 − BF% ÷ 100) Once body-fat percentage is known, fat mass and lean (fat-free) mass follow directly from your bodyweight.
Worked example: a man, 178 cm, neck 38 cm, waist 84 cm → 495 ÷ (1.0324 − 0.19077 × log₁₀(46) + 0.15456 × log₁₀(178)) − 450 ≈ 16.9% body fat. At 80 kg that's about 13.5 kg of fat and 66.5 kg of lean mass. Source: Hodgdon & Beckett, Naval Health Research Center, 1984.
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Open toolBody-fat questions.
How accurate is the US Navy body-fat method?
The US Navy circumference method estimates body fat within roughly 3 to 4 percentage points of a DEXA or hydrostatic reading for most people. It is far more accurate than BMI because it accounts for waist and neck size, but it is still an estimate — it assumes a typical fat-distribution pattern, so very lean or very heavy people can read off by more. Use it to track change over time rather than as an exact truth.
How do I measure my neck, waist, and hips correctly?
Use a flexible tape and keep it snug but not compressing the skin. Measure the neck just below the larynx, sloping slightly down to the front. Measure the waist at the navel for men and at the narrowest point for women. Women also measure the hips at the widest point of the buttocks. Take each measurement twice, relaxed, and average them for consistency.
What is a healthy body-fat percentage?
For men, the American Council on Exercise puts the fitness range at 14 to 17 percent and the athletic range at 6 to 13 percent; average is 18 to 24 percent. For women the equivalents run about 7 to 10 points higher because of essential fat needed for hormonal health: fitness 21 to 24 percent, athletic 14 to 20 percent, average 25 to 31 percent. Below the essential-fat floor is unsafe.
Why do men and women use different body-fat formulas?
Women naturally carry more essential fat and store it differently, so the US Navy method adds hip circumference to the female equation and uses different coefficients. Applying the male formula to a woman would badly underestimate her body fat. This calculator switches formulas automatically based on the sex you select.
Is body-fat percentage better than BMI?
For anyone who trains, yes. BMI only knows your height and weight and cannot tell muscle from fat, so it labels many lean, muscular lifters as "overweight". Body-fat percentage measures composition directly, so it stays meaningful whether you are muscular, lean, or somewhere between. Pair it with lean body mass and FFMI for the full picture.
Is this body-fat calculator free?
Yes. It computes entirely in your browser, updates as you type, and needs no signup. Save your result to Nishaana to track your body fat and lean mass alongside your training and nutrition over time.
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