Body Fat Calculator
The US Navy method
Developed in the 1980s by US Navy researchers, this method estimates body fat from a few circumference measurements. It needs only a tape measure and correlates reasonably well with laboratory methods. The metric formulas are:
- Men: 495 ÷ (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450
- Women: 495 ÷ (1.29579 − 0.35004 × log₁₀(waist + hips − neck) + 0.221 × log₁₀(height)) − 450
All measurements are in centimetres.
Worked examples
- A man, 180 cm, waist 85 cm, neck 38 cm: 16.1% body fat.
- A woman, 165 cm, waist 72 cm, hips 98 cm, neck 33 cm: 26.9% body fat.
How to read the result
The American Council on Exercise uses these categories:
| Category | Women | Men |
|---|---|---|
| Essential fat | 10–13% | 2–5% |
| Athletes | 14–20% | 6–13% |
| Fitness | 21–24% | 14–17% |
| Average | 25–31% | 18–24% |
| Obesity | 32% and above | 25% and above |
Women naturally carry more essential fat than men, which is why the ranges differ by about 8–10 points.
How to measure correctly
- Waist: men at the level of the navel; women at the narrowest point. Relaxed, after breathing out normally — don't pull your stomach in.
- Neck: just below the larynx (Adam's apple), with the tape sloping slightly downwards at the front.
- Hips (women): at the widest point of the buttocks.
- Keep the tape horizontal and snug without compressing the skin, measure each site twice and use the average.
Accuracy
Tape-measure methods typically land within about 3–4 percentage points of DEXA scans for most people, but they are less reliable for very lean or very heavy individuals. The best use is tracking: measure in the same conditions every few weeks and watch the trend. Combined with your BMI, it shows whether weight changes come from fat or muscle.
Frequently Asked Questions
Why do women need a hip measurement?
Women store more fat around the hips and thighs, so the female equation uses the hip circumference to capture it. The male equation does not need it.
How accurate is the US Navy body fat method?
It is usually within 3–4 percentage points of lab methods such as DEXA, which is good enough for tracking progress, but not for a precise diagnosis.
What is a healthy body fat percentage?
Roughly 14–24% for men and 21–31% for women falls in the 'fitness' and 'average' categories. Above 25% for men or 32% for women is classed as obesity.