Percent shortcuts
| 1% | Divide by 100 |
|---|---|
| 10% | Move the decimal point one place left |
| 5% | Half of 10% |
| 15% | 10% plus 5% |
| 25% | Divide by 4 |
| 50% | Divide by 2 |
Body Fat Estimate (US Navy Method)
Estimate body fat percentage from height, neck, waist (and hip for women) with the US Navy tape method. An estimate, not a medical test.
Calculator
How it works
Women enter hip as well; men need waist larger than neck.
Privacy
Local calculations
Most tools run directly in your browser. Your entered values are not sent to this Worker.
About the Body Fat Estimate (US Navy Method)
Estimate body fat percentage with the US Navy tape method: height, neck and waist for men, plus hip for women. It is cheaper than a lab scan and rough by design.
How to use it
Choose your equation and enter height, neck and waist in centimetres; women add hip.
Formula
Men: 495 ÷ (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450. Women: 495 ÷ (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450
Worked example
A man 180 cm tall with a 38 cm neck and an 84 cm waist is estimated at about 15.3% body fat.
Understanding your result
The headline is an estimated percentage with a broad category for this method. Track trends with the same routine, not single readings.
When it is useful
- Tracking change over months
- Adding a second view beside BMI
- Setting a starting point for training goals
Common mistake
Rushing the tape around the neck, waist or hip: measurement error can exceed real monthly change.
When to use it
A tape measure and a height are enough for the US Navy method, which estimates body fat from circumference ratios. It is useful as a trend: measured the same way, at the same time of day, once a month, the number moves in the right direction even if its absolute value is imperfect.
It is an estimate, not a laboratory measurement. Hydration, posture, where the tape sits and even a deep breath change the result, and the formulas were built on population averages rather than on you.
How the maths works
For men: 495 ÷ (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450. For women the constants differ and the hip is included: 495 ÷ (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450. All measurements are in centimetres.
The result is printed to one decimal and placed in a broad category for this method. For men the bands are under 6% essential fat, under 14% athletes, under 18% fitness, under 25% average; for women the same bands move to 14, 21, 25 and 32.
A worked example
A man 180 cm tall, neck 38 cm, waist 84 cm.
- Waist minus neck: 84 − 38 = 46.
- Logarithms: log10(46) = 1.6628 and log10(180) = 2.2553.
- Denominator: 1.0324 − 0.19077 × 1.6628 + 0.15456 × 2.2553 = 1.0637.
- 495 ÷ 1.0637 − 450 = 15.3%, in the fitness band.
The same man with a 95 cm waist lands near 21.9%, in the average band: ten centimetres of waist is worth about six points here.
Example readings
| Profile | Estimate | Category |
|---|---|---|
| Male, 180 cm, neck 38, waist 75 | 7.6% | Athletes |
| Male, 180 cm, neck 38, waist 84 | 15.3% | Fitness |
| Male, 180 cm, neck 40, waist 95 | 21.9% | Average |
| Female, 165 cm, neck 32, waist 70, hip 95 | 24.9% | Fitness |
| Female, 165 cm, neck 32, waist 65, hip 90 | 19.5% | Athletes |
Categories describe this method, not your health: the boundaries are arbitrary and a single reading says little about fitness.
Common mistakes
- Measuring in the wrong place. Neck below the larynx, waist at the navel, hip at the widest point, tape level and snug rather than tight.
- Measuring after exercise. Pumped muscles and a compressed waist shift the numbers; measure at rest, at the same time of day.
- Forgetting the hip for women. The female formula needs it, and the page refuses to guess.
- Comparing with a different method. A scale or a caliper will disagree; compare like with like, over months rather than days.
Keep exploring
- BMI Calculator — the simpler height-and-weight screening figure.
- Ideal Weight Calculator — formula weights and a BMI-based band.
- BMI Calculator (Imperial) — the same BMI in pounds and inches.
- Guide: BMI, Calories and Water Intake.
Frequently asked questions
How accurate is the tape method?
Typically within a few points of lab methods for consistent people, and worse when measurements are rushed.
Where should I measure?
Neck below the larynx, waist at the navel, hip at the widest point. The tape should be level and snug, not tight.
Is a lower number always better?
No. Below the essential-fat level health suffers, so aim for a range rather than a minimum.
A man 180 cm tall with a 38 cm neck and 84 cm waist: what is the estimate?
15.3% body fat. Waist minus neck is 46, and the formula returns 495 ÷ 1.0637 − 450 = 15.3.
How much does ten centimetres of waist change it?
About six points: the same man at 95 cm lands near 21.9%, moving from the fitness band to average.
A woman 165 cm, neck 32, waist 70, hip 95 — what does the method say?
24.9%, because the female formula adds waist and hip before subtracting the neck.
Why does the tool need the hip for women?
The female equation uses waist + hip − neck as its circumference term; without the hip the estimate would be a different formula.
Can I compare this with a smart scale?
Only loosely. The methods disagree by several points, so track one method consistently over months instead.
Page reviewed 21 October 2026. Results are estimates for general information. See the methodology and disclaimer.
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Every tool lists its formula and a worked example, so you can verify the answer yourself.
Understand the result
Each page explains how to read the result, when to use it and the mistakes to avoid.
Clear limits
Estimates are labelled as estimates. Read how we work on the methodology page.
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