Body Fat Calculator

1. Choose your sex and your units (metric or imperial).
2. Enter your height, neck and waist measurements (and hip for women).
3. Optionally add your weight to see fat mass and lean mass.
4. Read your body fat percentage and category.

Here is what each result means:

Body fat percentage is the proportion of your total body weight that is fat, as opposed to muscle, bone, organs and water. Two people can weigh the same yet look very different because one carries more fat and the other more muscle. Body fat percentage captures that difference in a way that weight alone, or even BMI, cannot.

This calculator uses the US Navy tape method, which estimates body fat from simple measurements of your height, neck and waist, plus your hip for women. It relies on the fact that fat tends to gather in predictable places, so the size of those areas relative to your height predicts body fat reasonably well without special equipment.

The result is an estimate, typically within a few percent of a clinical measurement such as a DEXA scan. It is most useful for tracking change over time: measuring the same way every few weeks shows whether you are losing fat or gaining muscle, which the bathroom scale can hide. It is a screening guide, not a medical diagnosis.

It applies the US Navy formulas, which use the base-10 logarithm of your measurements.

1. Measurements are converted to centimeters if you use imperial units.
2. The waist, neck and height (and hip for women) go into the formula for your sex.
3. The result is your estimated body fat percentage.

For related measures, see the BMI calculator and the waist to hip ratio calculator.

A man is 180 cm tall with a 38 cm neck and a 90 cm waist.

Calculation: the waist minus neck is 52 cm. Putting the logs of 52 and 180 into the men's formula gives a body fat of about 20 percent, which sits in the average range. Adding weight would also show the fat mass and lean mass in kilograms.

Healthy ranges differ for men and women because women carry more essential fat.

These American Council on Exercise ranges are a useful guide, not strict rules. Some essential fat is vital for health, so a very low body fat is not a goal for most people. The fitness and average bands cover the large majority of healthy adults.

Both screen for healthy weight, but they measure different things.

BMI is faster but can mislead for very muscular people, who may show a high BMI with low body fat. Body fat percentage avoids that by measuring fat more directly, so the two together give a fuller picture than either alone.

Measurement Accuracy

Use a snug, level tape and measure the same spots each time. Small errors change the estimate.

Sex

The formula and healthy ranges differ for men and women, so choose the correct sex.

Body Shape

The method assumes a typical fat distribution, so it is less accurate for unusual body shapes.

Tracking Progress

Measure every few weeks to see fat loss or muscle gain the scale can hide.

Setting Goals

Aim for a healthy category rather than just a target weight.

Fitness Planning

Understand your starting point before a training or nutrition program.

1. Measuring in the Wrong Place

Measure the neck below the larynx and the waist at the navel for men, the narrowest point for women.

2. Mixing Units

Keep all measurements in the same units and set the units toggle to match.

3. Choosing the Wrong Sex

Men and women use different formulas and ranges. The wrong choice skews the result.

4. Pulling the Tape Too Tight

A tape that is too tight or too loose changes the numbers. Keep it snug and level.

5. Treating It as Exact

It is an estimate. Use it to track trends, not as a precise clinical figure.

The US Navy method is a validated estimate, usually within a few percent of a clinical measurement.

It depends on sex. For men, the fitness range is about 14 to 17 percent and average is 18 to 24 percent. For women, fitness is about 21 to 24 percent and average 25 to 31 percent.

The US Navy method uses the log of your waist minus neck and your height for men, adding the hip for women. This calculator applies those formulas for you.

It is usually within about 3 to 4 percent of a clinical DEXA scan for most people. It is best for tracking change over time rather than as an exact figure.

Measure the neck just below the larynx, sloping slightly down at the front. Measure the waist at the navel for men and at the narrowest point for women.

Women store more fat around the hips, so the women's formula includes the hip to estimate body fat accurately. The men's formula does not use it.

Essential fat is the minimum needed for health, about 2 to 5 percent for men and 10 to 13 percent for women. Going below it can be harmful.

It is more informative because it separates fat from muscle. BMI is quicker but can misclassify very muscular people as overweight.

Yes. Set the units toggle to imperial and enter inches and pounds. The calculator converts your measurements internally.

No. The calculation runs in your browser and nothing you enter is stored or sent anywhere, unless you choose Save, which keeps the result only on this device.

• Body fat percentage (Wikipedia).
• US Navy body fat method (Wikipedia).
• Percent body fat norms (American Council on Exercise).