Body Fat % Calculator
Estimate your body fat percentage using the US Navy method — all you need is a flexible measuring tape.
What is the US Navy Body Fat Method?
The US Navy method is a circumference-based body fat estimation technique developed for military fitness assessments. It uses tape measurements of the neck, waist (and hips for women) along with height to estimate body fat percentage without expensive equipment.
The formula uses the natural logarithm of the circumference measurements to estimate lean and fat compartments. It was validated against hydrostatic weighing and shows a standard error of approximately ±3–4 percentage points for most individuals.
While not as accurate as DEXA scanning or hydrostatic weighing, the US Navy method is consistently reproducible, free, and accessible. It's the method used by the US military for fitness standards and is one of the most widely used field methods in fitness.
Body Fat Percentage Categories
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletic | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Acceptable | 18–24% | 25–31% |
| Obese | 25%+ | 32%+ |
How to Measure Correctly
Neck: Measure just below the larynx (Adam's apple), with the tape perpendicular to the long axis of the neck. Keep posture natural.
Waist (men): Measure at the level of the navel (belly button), horizontally, with a relaxed abdomen — not pulled in.
Waist (women): Measure at the narrowest point of the torso, typically just above the navel, horizontally.
Hip (women only): Measure at the widest point of the hips and buttocks, with feet together.
Frequently Asked Questions
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The US Navy method has a margin of error of approximately ±3–4 percentage points compared to gold-standard methods like DEXA or hydrostatic weighing. It performs best for people in the 10–30% body fat range and is less reliable at very low or very high body fat levels. Use it to track trends over time rather than as an absolute measurement.
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Women naturally carry more fat in the hips and thighs (gynoid distribution), so the hip measurement improves the formula's accuracy for women. Men tend to carry fat primarily in the abdomen (android distribution), so the waist measurement alone is sufficient.
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For men, the healthy range is generally 10–20% body fat. For women, it's 18–28%. These ranges are associated with good health outcomes. Athletes typically have lower body fat: 6–13% for male athletes and 14–20% for female athletes. Extremely low body fat (below essential fat levels) impairs hormone function and organ health.
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Monthly measurements are generally sufficient to track trends without being distracted by day-to-day fluctuations. Always measure at the same time of day (morning, before eating), under the same conditions, with the same tape measure for consistency.
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Body fat percentage is a more direct indicator of body composition than BMI. BMI cannot distinguish between fat and muscle, so a very muscular person may score "overweight" while having healthy body fat. However, body fat estimation methods have their own sources of error. Both metrics are useful, and neither should be interpreted in isolation.