📏 Body Fat Calculator
Estimate your body fat percentage from a few tape-measure readings using the US Navy formula.
Quick answer: The US Navy method estimates body fat from height, neck and waist (plus hips for women). A man 178 cm tall with a 38 cm neck and an 86 cm waist has about 17.2% body fat – the “fitness” range.
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Body Fat Calculator inputs
Result
Body fat (US Navy method)
17.2%
Fitness
| Fat mass | 13.8 kg |
| Lean body mass | 66.2 kg |
- ACE category
- Fitness
ACE body-fat categories
| Category | Men |
|---|---|
| Essential fat | 2–5% |
| Athletes | 6–13% |
| Fitness | 14–17% |
| Average | 18–24% |
| Obese | 25%+ |
The US Navy formula
Developed by Hodgdon and Beckett for the US Navy, this method estimates body density from circumference measurements, then converts density to body fat. All measurements below are in centimetres; the calculator converts inches automatically.
Men: %BF = 495 ÷ (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450
Women: %BF = 495 ÷ (1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.22100 × log₁₀(height)) − 450
Worked example
A man 178 cm tall with a 38 cm neck and 86 cm waist: waist − neck = 48 cm, so %BF = 495 ÷ (1.0324 − 0.19077 × 1.6812 + 0.15456 × 2.2504) − 450 ≈ 17.2%. At 80 kg that is 13.8 kg of fat and 66.2 kg of lean mass.
Body fat categories (ACE)
| Category | Women | Men |
|---|---|---|
| Essential fat | 10–13% | 2–5% |
| Athletes | 14–20% | 6–13% |
| Fitness | 21–24% | 14–17% |
| Average | 25–31% | 18–24% |
| Obese | 32%+ | 25%+ |
Measuring tips
- Use a flexible, non-stretch tape, snug but not compressing the skin.
- Measure in the morning before eating, relaxed, without sucking in.
- Take each measurement three times and use the average.
- Track the trend over weeks rather than chasing single readings.
Why body fat matters more than weight
Two people with the same height and weight can have very different health profiles. Body fat percentage separates fat from muscle, bone and water, so it shows whether weight changes come from fat loss or muscle gain. Fat stored around the waist is most closely linked with heart disease and type 2 diabetes, which is why the waist measurement carries so much weight in this formula.
For general information only – not medical advice. Consult a healthcare professional.
Frequently asked questions
How accurate is the US Navy body fat method?
Studies show it is typically within 3–4 percentage points of DEXA scans for most people. Accuracy depends heavily on measuring carefully and consistently.
Where exactly should I measure?
Measure the neck just below the larynx (Adam’s apple), sloping slightly down to the front. Men measure the waist at the navel; women at the narrowest point. Women measure hips at the widest point of the buttocks.
What is a healthy body fat percentage?
According to the American Council on Exercise, 14–24% is fit-to-average for men and 21–31% for women. Essential fat alone is about 2–5% for men and 10–13% for women.
Why do women need a hip measurement?
Women store more fat around the hips and thighs, so the female equation adds hip circumference to improve accuracy.