Free Body Fat Calculator — U.S. Navy Method + Body Fat Percentage (2026)
Estimate your body fat percentage free with the U.S. Navy tape method and a BMI-based cross-check. See your fat mass, lean mass, and category — then turn the number into a balanced plate.
Estimate your body fat percentage from a tape measure with the U.S. Navy method, cross-check it against the BMI-based formula, and see the fat mass and lean mass behind the number.
What is body fat percentage?
Body fat percentage is the share of your total weight that is fat — everything else (muscle, bone, water, organs) is your lean or fat-free mass. Two people can weigh the same and look very different because one carries more muscle and the other more fat, which is why body fat percentage is often a more useful read than weight or BMI alone.
A small amount of fat is essential: it cushions organs, stores energy, and (especially in women) supports hormone production. The rest is storage fat. The goal isn't the lowest possible number — it's a healthy range for your sex and life stage.
How the U.S. Navy method works
The U.S. Navy circumference method estimates body density from a few tape measurements — neck and waist for men, plus hips for women — together with your height, then converts that density to a fat percentage. It's the method the U.S. Department of Defense uses for fitness screening precisely because it needs nothing but a tape measure and is repeatable at home.
Against a gold-standard scan, the Navy estimate is typically accurate to within about 3–4 percentage points for most people. It can read high for very lean, muscular builds (a thick waist of muscle looks like fat to a tape) and is less reliable at the extremes — but for tracking change over time on the same body, it's hard to beat for free.
Body fat vs. BMI
BMI is just weight over height squared, so it can't tell muscle from fat. A lean athlete and a sedentary person can share a BMI while having very different body composition. That's the gap this page makes visible by showing the BMI-based estimate next to the Navy one.
The BMI-based figure here uses the Deurenberg formula, a population regression on BMI, age and sex. It's a reasonable sanity check, but it inherits BMI's blind spot for muscle — treat the Navy estimate as the primary number and the BMI one as context.
Healthy body fat ranges
Reference bands from the American Council on Exercise run from essential fat — the minimum the body needs — up through the athletic, fitness, and average ranges; the table above shows exactly where your result lands. Women carry more essential fat than men for the same level of leanness — that's biology, not a worse result.
Body fat also tends to drift up with age at the same weight as muscle is gradually lost, which is part of why protein intake and resistance activity matter more over time. These ranges are general guidance, not a diagnosis.
How to measure accurately
Use a flexible cloth or vinyl tape, keep it level and snug without compressing the skin, and measure on bare skin in the morning before eating. The hint under each input shows exactly where that measurement goes.
Measure each spot twice and average them — a half-inch difference on the waist can move the result by a point or more. Re-measuring the same way each time is what makes the trend trustworthy.
Formula & sources
U.S. Navy body density — men
U.S. Navy body density — women
Percent body fat from density (Siri)
All circumferences and height in centimetres.
BMI-derived estimate (Deurenberg)
A = age in years. Shown as a sanity-check against the Navy estimate.
Sources
- Hodgdon JA, Beckett MB (1984) Prediction of percent body fat for U.S. Navy men and women from body circumferences and height. Naval Health Research Center, reports 84-11 & 84-29.
- Deurenberg P, Weststrate JA, Seidell JC (1991) Body mass index as a measure of body fatness: age- and sex-specific prediction formulas. Br J Nutr 65(2):105–114.
- American Council on Exercise ACE body-fat percentage categories (essential, athletes, fitness, average, obese).
Body fat calculator FAQ
How accurate is this body fat calculator?
The U.S. Navy circumference method is typically within about 3–4 percentage points of a DEXA scan for most adults. It's most useful for tracking change on the same body over time; for one-off precision, a DEXA or hydrostatic test is the gold standard. The tape can read high for very muscular builds.
What is a healthy body fat percentage?
Using American Council on Exercise bands, the fitness range is roughly 14–17% for men and 21–24% for women, and the average range is about 18–24% (men) and 25–31% (women). Women need more essential fat than men (about 10–13% vs 2–5%) for normal hormone function, so a 'healthy' number is sex-specific.
Is the U.S. Navy body fat method reliable?
It's reliable enough that the U.S. Department of Defense uses it for fitness screening. It only needs a tape measure and your height, and it's repeatable at home. Its main limitation is that it estimates fat from circumference, so unusually muscular or unusually slim builds can skew it — which is why we also show a BMI-based estimate for comparison.
Why is my body fat different from my BMI?
BMI is only weight and height, so it can't separate muscle from fat — a muscular person can have a high BMI but low body fat. Body fat percentage measures composition directly (here, from tape measurements), which is why the two numbers can disagree. The Navy estimate is usually the better read of the two.
Where do I measure my neck, waist, and hips?
Neck: just below the larynx (Adam's apple), with the tape sloping slightly downward to the front. Waist: at the navel for men, at the narrowest point for women. Hips (women only): around the widest part of the buttocks. Keep the tape level and snug, measure on bare skin, and average two readings.
Can I lower my body fat percentage?
Yes — a modest, sustained calorie deficit paired with enough protein and resistance activity lowers fat while protecting lean mass. You can estimate a sensible deficit on our calorie-deficit calculator and turn your numbers into a balanced plate with the MyPlate Plan calculator.
Do I need calipers or a DEXA scan?
Not for an everyday estimate. Skinfold calipers and DEXA are more precise but need equipment or a clinic visit. The tape-measure method here is free, private, and — measured consistently — perfectly good for watching the trend over weeks and months.