Body Fat Percentage Calculator

Body fat percentage calculator at a glance#

How is body fat percentage calculated?#

The calculator above gives you two methods. The US Navy method uses tape measurements of your neck and waist (plus hips for women) and your height. The BMI method uses height, weight, age and sex. Pick one with the Method switch, and the result shows your body fat percentage, fat mass, lean mass and a category.

Can you calculate body fat from height and weight alone?#

Yes, that's what the BMI method does. It turns your BMI, age and sex into a body fat estimate with a formula from a 1991 study of 1,229 people. It's quick, but it can't tell muscle from fat, so it tends to read high for muscular people.

What is a good body fat percentage?#

On the bands this calculator uses, the fitness range is 21% to 24% for women and 14% to 17% for men. The average range is 25% to 31% for women and 18% to 24% for men. The women's bands sit higher than the men's at every level.

What body fat percentage means#

Body fat percentage is the share of your total weight that is fat. Everything else (muscle, bone, organs and water) is lean mass, the figure the BMR calculator's Katch-McArdle option builds on. Two people can weigh the same and have very different amounts of fat, which is why this number says more about body composition than the scale does.

One example runs through this page. A 35-year-old woman is 5 ft 5 in (165.1 cm) tall and weighs 140 lb (63.5 kg). Her neck measures 13 in (33.0 cm), her waist 29 in (73.7 cm) and her hips 39 in (99.1 cm). With the Navy method the calculator puts her at 28.3% body fat. That's 39.6 lb (17.9 kg) of fat and 100.4 lb (45.6 kg) of lean mass.

Method 1: the US Navy tape method#

The circumference equations were developed by James Hodgdon at the Naval Health Research Center on Navy sailors. The US military services later agreed on them as a common set of equations, as a 2022 paper in Frontiers in Physiology describes. The idea is simple: a waist that's large compared with your neck and height points to more fat around the middle.

The calculator works in centimeters. If you type inches, it converts them first (1 in = 2.54 cm). Then it finds your body density and turns density into a percentage:

• Women: density = 1.29579 − 0.35004 × log10(waist + hips − neck) + 0.22100 × log10(height)
• Men: density = 1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)
• Both: body fat % = 495 ÷ density − 450

Here's the example worked by hand:

1. Add the waist and hips and subtract the neck: 73.66 + 99.06 − 33.02 = 139.70 cm.
2. Take the base 10 logarithms: log10(139.70) = 2.1452 and log10(165.10) = 2.2177.
3. Find the density: 1.29579 − 0.35004 × 2.1452 + 0.22100 × 2.2177 = 1.0350.
4. Convert to body fat: 495 ÷ 1.0350 − 450 = 28.3%.

How to measure your neck, waist and hips#

Use a flexible tape on bare skin, stand relaxed and breathe out normally before you read the number. Wrap it around once and keep the tape level and snug, without pressing into the skin.

• Neck: just below the voice box (the Adam's apple), with the tape at a right angle to your neck.
• Waist for men: around the abdomen at the level of the navel.
• Waist for women: around the narrowest part of the waist.
• Hips (women only): around the widest part of the buttocks.
• Height: standing straight against a wall, without shoes.

Measure each spot twice. If the readings differ, measure a third time and use the average. Small errors matter here, because the waist minus neck difference drives the whole formula.

Method 2: the BMI method#

The BMI method uses the prediction formulas Paul Deurenberg and colleagues published in the British Journal of Nutrition in 1991. They measured body fat in 1,229 people aged 7 to 83 and fitted it against BMI, age and sex. The calculator first works out your BMI (weight in kg divided by height in meters squared) and then applies the adult formula:

• Women: body fat % = 1.20 × BMI + 0.23 × age − 5.4
• Men: body fat % = 1.20 × BMI + 0.23 × age − 16.2

For the example, BMI = 63.5 ÷ (1.651 × 1.651) = 63.5 ÷ 2.726 = 23.3, the same number the BMI calculator gives. Body fat = 1.20 × 23.3 + 0.23 × 35 − 5.4 = 30.6%.

For ages 15 to 17 the calculator switches to the study's formula for children: 1.51 × BMI − 0.70 × age + 1.4 for girls, with 3.6 subtracted for boys. The study fitted that one on children aged 15 and younger, so treat a teenager's result as a rough guide. The authors give a standard error of about 4.1 percentage points for adults and note the formula slightly overestimates body fat in people with obesity.

Why the two methods give different numbers#

The example woman gets 28.3% from the tape and 30.6% from her BMI. Neither is wrong. They look at different things. The Navy method reads your shape, so it notices a small waist. The BMI method only knows your weight for your height, age and sex, so a muscular person tends to come out fatter than they are.

Both are estimates. In the 2022 survey of US Marines, tape estimates ran about 2.5 points low for men and 1.3 to 2.3 points high for women compared with a DXA scan. The authors called the tape method useful for sorting people into categories but not precise enough for research. Pick one method, measure the same way each time, and watch the trend rather than a single reading.

Body fat percentage categories#

After it finds your percentage, the calculator rounds it to a whole number and places it in one of these bands. These are the calculator's own bands, not a medical standard. Their average range matches what a Verywell Health article in the American Council on Exercise (ACE) press room calls typical for the average nonathlete: 25% to 31% for women and 18% to 24% for men. The same article says below 14% for women or 6% for men may be dangerously low, which is the calculator's essential fat band.

On the women's scale below, the example lands in the average band with either method, at 28.3% from the tape and 30.6% from BMI.

This gives an estimate, not medical advice. A doctor can tell you what the number means for you.

The calculator also shows an ideal body fat for your age from a table built into the tool (21.5% for a 35-year-old woman). It also shows how much fat at your current weight separates you from that figure, 9.5 lb in the example. Treat it as a reference point, not a target set by a medical body. For weight ranges based on height instead, see the ideal weight calculator.

Other ways to measure body fat#

The tape and BMI methods are free and need nothing but a tape and a scale. Other options trade cost for precision.

• Skinfold calipers pinch the fat under the skin at several sites. They're cheap, but results depend a lot on who does the pinching.
• Bioelectrical impedance (BIA) scales send a weak current through your body and estimate fat from how it travels. They're easy to use daily, and the number can move with how much water you've had.
• A DXA scan, done in a clinic or lab, uses low-dose X-rays to map fat, lean tissue and bone. It was the reference method in the Marine study above.
• Underwater weighing measures body density directly, the same quantity the Navy formula estimates.

Body fat and the military standards#

People often look for this calculator when they face a military body fat check. Rules differ by service and change over time. The Army, for one, moved away from tape-measured body fat for soldiers in 2026, and the Army body fat calculator page explains the current standard and the older tape method.

Sources#

• Potter and colleagues, Circumference-Based Predictions of Body Fat Revisited: Preliminary Results From a US Marine Corps Body Composition Survey, Frontiers in Physiology, 2022
• Deurenberg, Weststrate and Seidell, Body mass index as a measure of body fatness: age- and sex-specific prediction formulas, British Journal of Nutrition, 1991
• Laura Dorwart, Body Fat Percentage: Charting Averages in Men and Women, Verywell Health, 2024 (in the ACE press room)

Frequently asked questions#

What is a healthy body fat percentage for women?#

On the calculator's bands, 21% to 24% is the fitness range for women and 25% to 31% is average. A result of 32% or more falls in the obese band. What counts as healthy for you also depends on your age and health, so a doctor is the right person to interpret it.

What is a healthy body fat percentage for men?#

For men the fitness range is 14% to 17% and the average range is 18% to 24%. The obese band starts at 25%. Men's bands sit lower than women's at every level.

Is the Navy body fat method accurate?#

It's a reasonable field estimate, not a lab result. Compared with DXA scans in US Marines, it read about 2.5 points low for men and 1.3 to 2.3 points high for women. Careful measuring matters most: in the example, a waist half an inch larger moves the result by about 0.6 points.

Which method should I use, Navy or BMI?#

Use the Navy method if you can take tape measurements, since it accounts for your shape. Use the BMI method when you only know your height and weight. If you're very muscular, expect the BMI method to read high.

How often should I check my body fat percentage?#

Every few weeks is usually enough to see a trend. Measure at the same time of day, before eating, with the same method each time. Day-to-day changes are mostly measuring noise.

Does the calculator work for teenagers?#

It accepts ages 15 to 80. In BMI mode it uses Deurenberg's children's formula up to age 17, and the Navy equations were built on adult sailors, so a teen's result is only a rough guide. A pediatrician can check growth and weight against age-based charts.