Enter your height, neck and waist measurements, plus hips for women, and your weight. The calculator estimates your body fat percentage, fat mass and lean mass.
Results are estimates for planning. Check the figures before you make a financial or health decision.
How the Body fat percentage works
The tool uses the US Navy method, which estimates body fat from tape measurements rather than weight alone. It uses a logarithmic formula based on height and the circumference of the neck and waist. For women, hip size is included as well.
- Men: the waist minus the neck, and height.
- Women: the waist plus hips minus the neck, and height.
It then applies the percentage to your weight to show fat mass and lean mass. It also names a category, using the American Council on Exercise ranges, from essential fat to above average. The ranges differ for men and women.
Measure the neck just below the Adam’s apple, the waist at the navel for men or the narrowest point for women, and the hips at their widest. Tape measurements can be a few percentage points out, and the tool shows an error if the figures give an impossible result. It is not as precise as clinical methods.
Worked example
Using the default values in the calculator above:
| Input | Value |
|---|---|
| Units | Metric (cm, kg) |
| Sex | Male |
| Height | 178 |
| Neck | 38 |
| Waist | 90 |
| Weight | 80 |
Estimated body fat: 20.1%
| Category | Average |
|---|---|
| Fat mass | 16.1 kg |
| Lean mass | 63.9 kg |
Tips and common mistakes
Measure at the same time of day, with the tape flat but not squeezing the skin, and repeat each measurement to check it. Use the result to track change over time rather than as an exact number. Combine it with BMI, waist size and how you feel. For a medical view of your body composition, speak to a health professional. General information, not medical advice.
Frequently asked questions
How accurate is the US Navy method?
It is a rough estimate and can be a few percentage points off. It is best used to track change with the same measuring technique each time.
Why do women need to enter hip size?
The formula for women uses waist, hips and neck together, as fat is distributed differently. Men do not need the hip measurement.
How is body fat different from BMI?
BMI only uses height and weight. Body fat uses body measurements to estimate the fat proportion, so it can distinguish muscle from fat better, though less exactly than a scan.
Guides that help
- Body fat percentage: how it's measured and what's typical
- BMI explained: what it tells you and what it doesn't