How does the US Navy method work?

It uses the logarithm of your height and tape measurements — neck and waist for men, plus hips for women — to estimate body-fat percentage without calipers or scales.

Why do women also measure their hips?

The female equation includes the hip circumference because fat distribution differs, which improves the estimate for women.

What is a healthy body-fat percentage?

It varies by sex and goals. The fitness and average bands — roughly 14–24% for men and 21–31% for women — are typical for healthy adults.

What are fat mass and lean mass?

Fat mass is your weight multiplied by your body-fat percentage; lean mass is everything else — muscle, bone, organs and water.

How can I measure accurately?

Use a flexible tape, keep it snug but not tight, measure at the right landmarks, and stay relaxed. Repeat each measurement and use the average.

Can I share my result?

Yes. Use Share to copy a link that reopens the calculator with the same measurements and units.

Body fat calculator

Enter your sex, height and a few tape measurements to estimate your body-fat percentage, category and fat/lean mass as you type.

The US Navy method estimates body fat from your height and the circumference of your neck and waist (and hips for women) — no special equipment needed.

Units

Sex

Height

Neck

Waist

Weight

Body fat

19.8 %

Average

Fat mass: 15.8 kgLean mass: 64.2 kg

The bar shows where your body fat sits on a 0–45% scale, and the category compares it to ACE fitness ranges for your sex.

How does it work?

Women use waist + hip − neck and different constants. Imperial entries are converted to centimetres first.

US Navy body-fat formula (men)

\text{BF\%} = \dfrac{495}{1.0324 - 0.19077\log_{10}(\text{waist} - \text{neck}) + 0.15456\log_{10}(\text{height})} - 450

waist: Waist circumference in centimetres.
neck: Neck circumference in centimetres.
height: Standing height in centimetres.

A man 180 cm tall with a 90 cm waist and 38 cm neck has a body fat of about 20%.

Expert tips

Circumference estimates are less precise than methods like DEXA or hydrostatic weighing.
Results are an estimate for healthy adults, not a medical assessment.

Method & sources

Body fat is estimated with the US Navy circumference method and grouped with American Council on Exercise (ACE) ranges. The ACE reference below explains those categories. You take the tape measurements — the calculator does not scan or diagnose body composition.

Sources

Where this method comes from — use these references to understand the formula, assumptions, and limits.

Percent body fat calculator — ACE fitness categories — American Council on Exercise, verified 2026-06-10

How we calculate

Uses the US Navy circumference method: neck and waist for men, plus hip for women, with height.
Categories follow the American Council on Exercise (ACE) ranges, which differ for men and women.
Accuracy depends on careful, snug tape measurements taken at the right landmarks.

Limitations

Circumference estimates are less precise than methods like DEXA or hydrostatic weighing.
Results are an estimate for healthy adults, not a medical assessment.

Rounding

Body fat is shown to one decimal place. Imperial tape measurements are converted to centimetres before the metric US Navy formula is applied, and fat and lean mass are reported in the weight unit you entered.

What this calculator does

Body-fat percentage is the share of your weight that is fat. This calculator uses the US Navy circumference method — a tape measure and your height — to estimate it, then splits your weight into fat mass and lean mass.

How to measure

Neck: just below the larynx, tape sloping slightly down at the front.
Waist: men at the navel, women at the narrowest point.
Hip (women): around the widest part of the buttocks.
Keep the tape snug and level, and measure relaxed, not breathing in.

Fitness categories

Results are grouped using ACE ranges. For men: essential 2–5%, athletes 6–13%, fitness 14–17%, average 18–24%, obese 25%+. For women: essential 10–13%, athletes 14–20%, fitness 21–24%, average 25–31%, obese 32%+.

A worked example

A man 180 cm tall with a 90 cm waist and 38 cm neck has a body fat of about 20%, in the average range. At 80 kg that is roughly 16 kg of fat and 64 kg of lean mass.

How accurate is it?

The tape method is convenient and reasonably consistent over time, but less precise than lab methods such as DEXA. Take measurements the same way each time to track changes reliably.

FAQ

How does the US Navy method work?: It uses the logarithm of your height and tape measurements — neck and waist for men, plus hips for women — to estimate body-fat percentage without calipers or scales.
Why do women also measure their hips?: The female equation includes the hip circumference because fat distribution differs, which improves the estimate for women.
What is a healthy body-fat percentage?: It varies by sex and goals. The fitness and average bands — roughly 14–24% for men and 21–31% for women — are typical for healthy adults.
What are fat mass and lean mass?: Fat mass is your weight multiplied by your body-fat percentage; lean mass is everything else — muscle, bone, organs and water.
How can I measure accurately?: Use a flexible tape, keep it snug but not tight, measure at the right landmarks, and stay relaxed. Repeat each measurement and use the average.
Can I share my result?: Yes. Use Share to copy a link that reopens the calculator with the same measurements and units.

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