Calculate body fat percentage using the US Navy Method — a scientifically validated formula used by the US military. Find your healthy body fat range for men and women in metric or imperial units.
US Navy Method — clinically validated
The US Navy Method is the circumference-based body fat percentage formula officially used by the United States military. It requires only a tape measure — neck, waist, and hips (for women) — making it one of the most accessible and validated methods for estimating body fat without expensive equipment like DEXA scans, hydrostatic weighing, or BOD POD testing. For most adults, it estimates body fat within 3–4 percentage points of lab methods, which is accurate enough to set realistic fitness goals and track progress over months. According to the American Council on Exercise (ACE), essential fat for women is 10–13% and for men is 2–5% — going below these levels carries serious health risks.
The CDC reports that roughly 41.9% of American adults have obesity, defined by the NIH as a BMI over 30 — but BMI doesn't distinguish fat from muscle. Body fat percentage is a more informative metric because a 200-pound athlete at 12% body fat and a sedentary person at 25% body fat both have the same weight, but very different health profiles. Setting a realistic goal — say, dropping from 28% to 20% body fat — is more actionable than chasing a number on a scale. Combined with a calorie deficit and resistance training, tracking body fat percentage helps you preserve lean muscle while losing fat, which is exactly what drives lasting body composition change.
Men: 2–5% | Women: 10–13%. The minimum level needed for hormonal function, organ protection, and survival. Dropping below essential fat is associated with serious metabolic and hormonal disruption.
Men: 6–13% | Women: 14–20%. Typical for competitive athletes, runners, cyclists, and bodybuilders. Achieving this range usually requires disciplined nutrition and regular strength or cardio training.
Men: 14–17% | Women: 21–24%. Lean and healthy — the sweet spot for most gym-goers and active adults. Visible muscle definition is common at the lower end of these ranges.
Men: 25%+ | Women: 32%+. Associated with significantly elevated risk of type 2 diabetes, cardiovascular disease, sleep apnea, and joint problems. Even a 5% reduction in body fat produces measurable health improvements.
The US Navy circumference method estimates body fat from tape measurements rather than calipers or scanning, which is why it spread beyond the military — it needs no equipment and is repeatable by one person alone. It works because fat distribution is statistically predictable: the ratio of waist to neck circumference, scaled against height, correlates well with total adiposity across large populations. Accuracy is roughly ±3–4 percentage points against hydrostatic weighing, which is good enough to track change over time and too coarse to treat a single reading as precise. Measurement technique matters more than the formula: taping at a different height on the abdomen can move the answer by several points.
Men: BF% = 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76Women: BF% = 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387all circumferences in centimetreswhere:
Assumptions: Validated on adults and less reliable at the extremes of body composition. Measure at the same time of day, unclothed and before eating, and take the average of three readings — day-to-day variation in technique easily exceeds real change.
Height 178 cm, waist 92 cm, neck 39 cm — worked through the logarithms explicitly.
ResultBody fat ≈ 27.4%
Losing 5 cm from the waist with the neck unchanged moves this to 23.7% — the formula is sensitive enough to track real progress. Because it is a logarithmic relationship, the same 5 cm matters more at a smaller waist than at a larger one.