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Body Fat Percentage Calculator
Estimate your body fat percentage using the US Navy circumference method. Enter your measurements to see an estimate of how much of your weight is fat.
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Estimated body fat %
How body fat is estimated
The US Navy circumference method estimates body fat percentage using measurements of your neck and waist (men) or neck, waist, and hips (women). The formula was developed by the US Navy in the 1940s as a practical field method to estimate body composition without specialized equipment. It correlates with DEXA scans (the gold standard for body composition measurement) at approximately r = 0.85, meaning it explains about 72% of the variance in actual body fat — reasonably accurate for a tape-measure method, but not precise enough for medical diagnosis. The measurement sites are standardized: measure the neck just below the larynx (Adam's apple), the waist at the narrowest point (typically at or above the navel), and for women, the hips at the widest point. Measurements should be taken with a flexible but non-stretchable tape measure, against skin or thin clothing, at the end of normal exhalation.
Body fat categories (Essential, Athletes, Fitness, Average, Obese) are based on epidemiological research linking body fat percentage to health outcomes across populations. These categories are useful benchmarks but have significant limitations: athletes with very low body fat may be categorized as "essential" despite being extremely healthy, and elderly individuals may fall in the "average" category despite having concerning visceral fat distributions that the category does not capture. Body fat percentage is only one component of body composition — two people at the same body fat percentage can look very different depending on their muscle mass, bone density, and where fat is stored.
Frequently asked questions
How accurate is the US Navy body fat formula?
The US Navy method correlates with DEXA scans at approximately r = 0.85, which means it explains about 72% of the variance in actual body fat — reasonable for a field method but not as accurate as DEXA, bioimpedance, or hydrostatic weighing. Measurement error is the largest source of inaccuracy: even 1 cm of error in waist or neck measurement can shift the body fat estimate by 1-2 percentage points. The formula was developed from data on young military personnel and may be less accurate for older adults, very obese individuals, or people with unusual body compositions. Use it as a consistent tracking tool rather than a precise diagnostic measure.
How often should I measure body fat?
Body fat percentage changes slowly — expect to see meaningful shifts only after 4-8 weeks of consistent training and nutrition changes. Weighing yourself daily and body-fat checking weekly is reasonable. Because measurement error (particularly in waist circumference) can be larger than the actual change over short periods, tracking trends over 4-6 week intervals is more informative than single measurements. Always measure at the same time of day, in the same state of hydration, and using the same measurement technique for consistency.
What body fat percentage should I aim for?
Target body fat percentages depend on your sex, age, and goals. For men: essential fat is 2-5% (minimum for organ function), athletes typically 6-13%, fitness 14-17%, average 18-24%, obese 25%+. For women: essential fat is 10-13%, athletes 14-20%, fitness 21-24%, average 25-31%, obese 32%+. These ranges are based on population health research, not individual optimization. If you are an endurance athlete, lower body fat improves performance. If you are primarily interested in general health, staying within the athlete or fitness range for your sex is associated with the best health outcomes. Very low body fat levels maintained long-term can impair immune function, cause hormonal disruptions, and reduce bone density.
Why does body fat distribution matter?
Where your body stores fat matters more than the total amount for many health outcomes. Visceral fat (fat stored around organs in the abdomen) is metabolically active and associated with increased risk of cardiovascular disease, type 2 diabetes, and metabolic syndrome. Subcutaneous fat (fat under the skin, particularly in the hips and thighs) is less metabolically harmful and is more common in women due to estrogen's effect on fat distribution. The waist-to-height ratio and waist circumference are better predictors of metabolic health than body fat percentage alone — a man with 20% body fat stored primarily in his hips and thighs is healthier than a man with 18% body fat stored primarily in his abdomen, despite having a higher body fat percentage.
How is body fat different from BMI?
BMI estimates whether your weight is appropriate for your height but says nothing about body composition. A muscular athlete with 10% body fat and 90 kg of lean mass at 185 cm has a BMI of 26.3 (technically "overweight"), yet clearly has very little excess fat. A frail elderly person at 70 kg with 35% body fat at 175 cm has a BMI of 22.9 (normal) but carries significantly more dangerous visceral fat. Body fat percentage directly measures the thing you are actually trying to assess (fat mass relative to total weight), while BMI is a proxy that is confounded by muscle mass, bone density, and fat distribution.
Does the formula work for all ethnicities?
The US Navy formula was developed from data on young white and Black military personnel in the 1940s-1980s. Research suggests the formula may underestimate body fat in Asian populations by 2-4 percentage points and may have similar accuracy issues for other ethnic groups. Ethnic differences in body composition — including bone density variations and fat distribution patterns — are not captured by the formula. For non-white adults, the body fat estimate should be treated as approximate, and trends over time are more informative than absolute values.
Can I use this if I am pregnant or breastfeeding?
No — the US Navy body fat formula was not developed for and is not validated for use during pregnancy or breastfeeding, when body composition changes substantially. Pregnant and breastfeeding women have expanded blood volume, breast tissue, and fluid stores that will distort the circumference measurements and produce inaccurate results. Body fat measurement during pregnancy should be done under medical supervision using appropriate clinical methods.
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For general wellness information only, not medical advice — see our disclaimer.