Free body fat calculator using the U.S. Navy tape method. Estimate your body fat percentage from neck, waist, hip, and height in cm or inches.
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Body fat percentage is often a better health indicator than weight or BMI, because it separates fat mass from muscle and bone. This calculator uses the U.S. Navy circumference method—a validated tape-measure technique used by the military—so you can estimate your body fat at home in seconds, no calipers or lab scan required. Enter measurements in centimeters or inches; results update live and show which body-composition category you fall in.
The Navy method estimates body fat from the circumference of your neck and waist (plus hips for women) relative to your height. Because fat and lean tissue distribute differently around the body, these girths predict body-fat percentage with a standard error of about 3–4% against hydrostatic weighing—far closer than BMI, which cannot tell muscle from fat. It is not as precise as a DEXA scan, but it is free, repeatable, and excellent for tracking change over time. This calculator applies the canonical metric (centimeter) formulas, so results are accurate whether you measure in cm or inches.
Navy Method (metric, cm)
Dieting lifters use it to confirm the scale drop is fat, not hard-earned muscle, and to know when to stop cutting before hitting the essential-fat floor.
When weight plateaus, a falling body-fat percentage proves the program is still working, keeping motivation up through the stall.
Combat-sport and rowing athletes gauge how much fat they can safely lose to make a class without sacrificing performance or dipping into unhealthy territory.
High body fat, especially around the waist, correlates with cardiovascular and metabolic risk. Tracking it flags a problem BMI can hide in normal-weight individuals.
BMI labels many muscular people 'overweight' and misses skinny-fat individuals. Body fat percentage measures composition directly, so it reflects real health risk far better than weight alone.
All you need is a flexible tape measure. There is no need for skinfold calipers, bioelectrical scales, or an expensive DEXA appointment to get a usable number.
The scale can stall while you lose fat and gain muscle. Re-measuring monthly shows whether your training and diet are changing composition, not just body weight.
Knowing your current category (essential, athlete, fitness, average, obese) and the healthy range for your sex helps you set a target body-fat percentage instead of an arbitrary goal weight.
For men, roughly 6–17% is athletic-to-fit, 18–24% is average, and 25%+ is obese; essential fat is 2–5%. For women, 14–24% is athletic-to-fit, 25–31% is average, and 32%+ is obese; essential fat is 10–13%, higher than men because of reproductive and hormonal needs. Dropping below essential fat is unhealthy.
It has a standard error of about 3–4% body fat versus underwater weighing—less precise than a DEXA scan but far better than BMI, and more than accurate enough to track your own trend over weeks and months. Consistent measuring technique matters more than absolute precision.
Use a flexible (cloth or fiberglass) tape. Measure your neck just below the larynx, your waist at navel level (men) or narrowest point (women), and hips at the widest point (women). Keep the tape level and snug but not compressing the skin, breathe out normally, and measure at the same time of day each session for comparable results.
Women carry more fat around the hips and thighs, so the female Navy formula adds hip girth to capture it. Without the hip measurement the estimate would be badly off, which is why hips are required for women and not requested for men.
Either—each field has its own cm/in toggle and the calculator converts everything to centimeters before applying the canonical metric formula, so you get the same accurate result no matter which units you use. Just be consistent between sessions.