Body Fat Calculator

Typically within 3-4% of hydrostatic weighing when tape measurements (neck, waist, hip) are taken consistently. Less accurate for very lean athletes or unusual body proportions.

Men: 14-24% healthy, 6-13% athlete. Women: 21-31% healthy, 14-20% athlete. Essential fat is ~2-5% (men) and ~10-13% (women).

Navy uses actual circumferences so it reflects fat distribution and is generally more accurate for individuals. BMI method cannot distinguish muscle from fat and overestimates for muscular people.

Yes, the Body Fat Calculator is 100% free with no registration, no hidden fees, and no usage limits. All processing happens locally in your browser, ensuring complete privacy.

Absolutely. The Body Fat Calculator processes everything client-side in your browser. No data is uploaded to or stored on any server. Your content remains private on your device at all times.

Yes, the Body Fat Calculator is fully responsive and works on smartphones and tablets. You can use it on any device with a modern web browser -- no app download required.

No account or registration is needed. Simply open the Body Fat Calculator in your browser and start using it immediately. There are no sign-up walls or usage restrictions.

Simply enter your input in the provided field, adjust any settings to your preference, and the tool will process it instantly. You can then copy the result to your clipboard or download it.

The Body Fat Calculator works in all modern browsers including Chrome, Firefox, Safari, Edge, and Opera. For the best experience, use the latest version of your preferred browser.

The US Navy formula is only as reliable as your tape work, so use a flexible tape pulled snug but not pressing into the skin, and take each reading two or three times. Measure the neck just below the larynx (Adam's apple) with the tape sloping slightly downward at the front. For the waist, men measure at the navel, while women measure at the narrowest point. Women also measure the hip at its widest point; men skip this entirely. Stand relaxed, breathe normally, and avoid measuring right after eating or exercising. Because the formula is logarithmic, small tape errors shift the result, so consistency matters more than perfection. Enter these circumferences along with your height, weight, age, and sex, and the calculator returns your body fat percentage instantly.

Fat mass is the portion of your weight made up of body fat, while lean body mass is everything else: muscle, bone, organs, and water. Together they add up to your total weight, so if you weigh 80 kg at 20% body fat, that is 16 kg of fat mass and 64 kg of lean body mass. Tracking these two numbers separately is far more useful than watching the scale, because it shows whether weight changes come from fat or muscle. During a recomposition phase you might hold the same weight while fat mass falls and lean mass rises, which the scale alone would hide. This calculator splits your weight into both figures in kilograms and pounds and shows a visual lean-versus-fat bar so you can see the breakdown at a glance.

Healthy body fat percentage naturally rises as you get older, so a single fixed target would mislead people across different decades. With age, the body tends to lose muscle mass and gain fat even at a stable weight, and a modestly higher percentage in your fifties can be perfectly healthy where the same number might be high for someone in their twenties. That is why this calculator shows an age-group ideal range rather than one universal figure, shifting the target across decades for your sex. For broad reference, commonly cited healthy ranges are roughly 14 to 24 percent for men and 21 to 31 percent for women, but the age-adjusted band gives a fairer benchmark. Enter your age and sex and the tool displays the range that actually applies to you.

BMI is calculated only from height and weight, so it has no way to tell whether your weight is muscle or fat. Because muscle is denser than fat, a lean, heavily trained athlete can carry a lot of weight in a compact frame and land in the overweight or even obese BMI band despite having low body fat. Body fat percentage avoids this trap by measuring composition directly through tape measurements, so it reflects how much of your weight is actually fat. This calculator shows the Navy circumference estimate as the headline figure for exactly this reason, with a BMI-based Deurenberg estimate alongside for comparison. The gap between the two is often largest for muscular people, which is precisely when the body fat number tells the more honest story. Enter your measurements to see both side by side.

You can use either. A toggle lets you switch between metric (kilograms and centimeters) and imperial (pounds and inches) at any time, so you enter measurements in whatever units your tape and scale already use. The calculator converts everything internally, meaning you never have to do manual unit math or look up conversion factors yourself, and switching units mid-session does not change your underlying result. This is handy if you bought a tape marked in inches but track weight in kilograms, or vice versa. Results are then displayed with lean body mass and fat mass shown in both kilograms and pounds regardless of which input mode you chose, so the figures are easy to read in your preferred system. Pick your units, enter your height, weight, age, sex, and circumferences, and read your body fat percentage right away.