Body Fat Calculator
Estimate your body fat percentage from a few tape measurements, using the US Navy method.
US Navy circumference method ยท By Stuart Mathieson · Updated October 2026
Height
To show fat mass and lean mass
Results
Estimated body fat
Fat Mass
Lean Mass
Tape-measure estimates are approximate and are not a medical assessment. Talk to a healthcare provider about your health.
How the body fat calculator works
The US Navy method estimates body fat from your height and a few circumferences around the neck and middle. It was developed by Hodgdon and Beckett at the Naval Health Research Center in 1984, and the US Department of Defense has used these equations for military body composition checks. They work in inches, so metric measurements are converted first (1 inch = 2.54 cm):
If you enter your weight, the calculator also splits it into fat mass (weight × body fat %) and lean mass - everything else, including muscle, bone and water.
Worked examples
- A man 178 cm tall with a 38 cm neck and an 86 cm waist: 17.3%, in the fitness range. At 75 kg, that is about 13.0 kg of fat and 62.0 kg of lean mass.
- The same idea in US units - 70 in tall, 15 in neck, 34 in waist: 17.5%.
- A woman 165 cm tall with a 33 cm neck, 74 cm waist and 99 cm hips: 28.7%, in the average range.
How to measure
- Use a tape measure that doesn't stretch, and keep it level - parallel to the floor.
- Pull it snug against the skin without pressing into it.
- Neck: just below the larynx (Adam's apple).
- Waist: men at the navel; women at the narrowest part of the abdomen.
- Hips (women): around the widest part of the hips and buttocks.
- Take each measurement three times and use the average - the military procedure does the same.
Body fat categories
The American Council on Exercise (ACE) uses these ranges:
| Category | Women | Men |
|---|---|---|
| Essential fat | 10-13% | 2-5% |
| Athletes | 14-20% | 6-13% |
| Fitness | 21-24% | 14-17% |
| Average | 25-31% | 18-24% |
| Obese | 32% and above | 25% and above |
How accurate is it?
Tape-measure methods are estimates. In a 2022 study of US Marines, the Navy equations averaged about 2.5 percentage points below a DXA scan for men and about 1.3 to 2.3 points above it for women, and individual results varied more than that. They tended to overestimate body fat in lean people and underestimate it in people with more body fat.
So treat the result as a rough guide rather than a precise measurement, and measure the same way each time if you compare results. It isn't designed for children or for use during pregnancy. For a quick check based on height and weight alone, see the BMI Calculator.
Frequently asked questions
How accurate is the US Navy body fat method?
It gives an estimate, typically within a few percentage points. A 2022 study of US Marines found it averaged about 2.5 points below a DXA scan for men and 1.3 to 2.3 points above for women, overestimating lean people and underestimating people with more body fat.
Why does it need my neck measurement?
The equations subtract the neck from the waist (and hips) to allow for body size - a larger neck generally goes with a larger frame and more muscle, rather than more fat around the middle.
Is body fat percentage better than BMI?
It measures something BMI can't - how much of your weight is fat - so a muscular person who scores as overweight on BMI may have a healthy body fat level. Tape estimates have their own error, though, so the two work best together.
What is a healthy body fat percentage?
On the American Council on Exercise ranges, average is 25-31% for women and 18-24% for men, and the fitness range is 21-24% for women and 14-17% for men. Healthy levels also vary with age.
Sources
- Prediction of percent body fat for U.S. Navy men from body circumferences and height - Hodgdon JA, Beckett MB, Naval Health Research Center Report 84-11, 1984
- Circumference-Based Predictions of Body Fat Revisited: Preliminary Results From a US Marine Corps Body Composition Survey - Potter AW et al., Frontiers in Physiology, 2022
- Anthropometric Measurements: When to Use this Assessment - American Council on Exercise