Free health tool
Body Fat Calculator
Estimate your body fat percentage using the US Navy circumference method. You only need a tape measure — no specialist equipment required.
Estimate your body fat
Measure at the widest point. All measurements in cm.
How to use this calculator
- Select your gender — the formula and required measurements differ for men and women.
- Measure your height standing straight, barefoot.
- Measure your waist at the navel (men) or narrowest point (women), after a normal exhale.
- Measure your neck just below the Adam's apple, keeping the tape horizontal.
- If female, measure your hip at the widest point.
- Enter all values in cm and click Calculate Body Fat.
US Navy body fat method
The US Navy circumference method estimates body fat percentage using body measurements rather than weight and height alone. It was developed as a practical, low-cost screening tool and is widely used when more precise methods like DEXA scans are unavailable.
Men
% fat = 495 / (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450
Women
% fat = 495 / (1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.22100 × log₁₀(height)) − 450
Example (male, height 180 cm, waist 85 cm, neck 38 cm)
log₁₀(85−38) = log₁₀(47) ≈ 1.672
log₁₀(180) ≈ 2.255
495 / (1.0324 − 0.19077×1.672 + 0.15456×2.255) − 450 ≈ 16.8%
Body fat categories
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletes | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Obese | 25%+ | 32%+ |
Source: American Council on Exercise (ACE)
Limitations
- Accuracy is approximately ±3–4% compared to DEXA — much less precise than clinical body composition methods.
- Measurement error compounds quickly. An error of 1–2 cm in the waist or neck can shift the result by 1–2%.
- The formula was developed on a specific military population and may be less accurate for other demographic groups.
- It does not account for the distribution of fat between subcutaneous (under skin) and visceral (around organs) — visceral fat carries higher health risk.
- Results should not be used for medical or fitness decisions without professional assessment.
Frequently asked questions
How accurate is the US Navy body fat method?+−
The US Navy circumference method has a reported error of approximately ±3–4% body fat compared to DEXA scans. Accuracy depends heavily on correct measurement technique — measuring at the wrong location or with clothing on can introduce significant error.
Where exactly should I measure my waist?+−
For men, measure the waist at the level of the navel. For women, measure at the narrowest point of the abdomen, usually just above the navel. Use a flexible tape measure, keep it horizontal, and measure after a normal exhale — do not suck in.
Where should I measure my neck?+−
Measure the neck just below the larynx (Adam's apple), keeping the tape perpendicular to the spine. The neck measurement should be taken with the head in a neutral position, not tilted.
Why is the hip measurement only needed for women?+−
The US Navy formula for women includes hip circumference because women typically carry more fat in the hip region. The male formula uses only waist and neck because fat distribution patterns differ significantly between sexes.
Is body fat percentage more useful than BMI?+−
For assessing body composition, yes — body fat percentage tells you directly how much of your weight is fat tissue. BMI cannot distinguish fat from muscle. However, body fat measurements from circumference methods are still estimates and are less precise than clinical methods like DEXA.
What is a healthy body fat percentage?+−
According to the American Council on Exercise (ACE), fitness-range body fat is roughly 14–17% for men and 21–24% for women. Essential fat — the minimum needed for basic health — is about 2–5% for men and 10–13% for women. These are general ranges, not clinical targets.
References
Health disclaimer
This calculator is for general informational purposes only and does not replace professional medical advice. Always consult a qualified healthcare provider for personal health concerns.