Body Fat Calculator
Estimate your body fat percentage in seconds using the trusted U.S. Navy tape method or a quick BMI-based estimate. See your fat mass, lean body mass, your body-fat category, and exactly where you sit on the scale. Works in metric and imperial.
Pick a method, enter your measurements, and see your body fat percentage, fat mass, lean mass, and category. The U.S. Navy method needs a tape measure; the BMI method needs only height, weight and age.
* Body fat percentage here is an estimate, not a direct measurement. The U.S. Navy tape method and BMI method both carry an error margin of a few percentage points and are less reliable for very muscular or very lean people. Gold-standard methods such as DEXA scans or hydrostatic weighing are more accurate. This tool is for general information only and is not medical advice — talk to a qualified professional for guidance tailored to you.
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What Is a Body Fat Calculator?
A body fat calculator estimates what percentage of your body weight is fat, rather than muscle, bone, water, and organs. Unlike BMI, which only relates weight to height, body fat percentage describes your actual body composition — and that's often a more useful picture of fitness and health.
This tool offers two popular estimating methods. The U.S. Navy method uses simple tape-measure circumferences (neck, waist, and hip for women) plus your height. The BMI method estimates body fat from your height, weight, age and sex when you don't have a tape handy. Both work in metric and imperial.
How to Use This Body Fat Calculator
- Choose your units and sex — the formulas differ for men and women.
- Pick a method — Navy (tape measure) for the better estimate, or BMI if you only have height, weight and age.
- Enter your measurements — for the Navy method, measure your neck below the larynx, your waist at the navel, and (for women) your hips at the widest point.
- Add your weight — so the calculator can also show your fat mass and lean mass.
Click Calculate Body Fat to see your percentage, category, body composition, and where you land on the scale.
The Body Fat Formulas
The U.S. Navy method uses logarithmic circumference equations (all measurements in centimetres):
BF% = 495 ÷ [1.0324 − 0.19077·log₁₀(waist − neck) + 0.15456·log₁₀(height)] − 450
Women:
BF% = 495 ÷ [1.29579 − 0.35004·log₁₀(waist + hip − neck) + 0.22100·log₁₀(height)] − 450
The BMI method (Deurenberg equation) estimates body fat from BMI, age and sex:
(sex = 1 for men, 0 for women)
Once body fat percentage is known, fat mass = weight × BF% and lean mass = weight − fat mass.
Body Fat Percentage Categories
The American Council on Exercise (ACE) describes these general ranges:
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletes | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average / acceptable | 18–24% | 25–31% |
| Obese | 25%+ | 32%+ |
Body Fat Percentage vs BMI
BMI is quick, but it can't tell muscle from fat. A muscular athlete and someone carrying excess fat can share the same BMI while having very different bodies. Body fat percentage looks past total weight to what that weight is made of, which is why athletes, lifters, and anyone tracking a recomposition often prefer it. The trade-off is that body fat is harder to measure precisely — estimates like these are convenient, but a DEXA scan is the gold standard.
What Affects Body Fat Percentage?
- Sex: women naturally carry more essential fat than men.
- Age: body fat tends to rise gradually with age, even at a steady weight.
- Muscle mass: more muscle lowers your body fat percentage at the same weight.
- Genetics & hormones: influence where and how much fat you store.
Tips for a Healthy Body Composition
- Build the habit, not the obsession. Consistent movement and balanced meals matter more than any single reading.
- Include strength training. Preserving muscle improves composition even when weight is steady.
- Measure the trend. Re-measure every few weeks under the same conditions, not daily.
- Use it alongside other signals — energy, strength, how clothes fit, and professional advice.