What is body fat percentage?
Body fat percentage tells you what share of your body mass is fat tissue. Unlike body mass index (BMI), it separates fat from muscle, bone and water, so for athletes or people with a lot of muscle mass it is the more telling number. Some fat is essential: it stores energy, surrounds organs and is part of how hormones work.
The World Health Organization (WHO) uses BMI to assess body weight, and body fat percentage often adds to the picture. The American Council on Exercise (ACE) publishes a scale, which this calculator also uses. What counts as a typical range depends on sex and age, and women naturally carry a higher percentage than men. That is why the numbers are best compared with your own results over time, not with other people.
| Category | Women | Men |
|---|---|---|
| Essential fat | 10–13 | 2–5 |
| Athletes | 14–20 | 6–13 |
| Fitness | 21–24 | 14–17 |
| Average | 25–31 | 18–24 |
| High percentage | 32 and over | 25 and over |
How the US Navy method works
The method was developed for the US Navy to estimate body fat without special equipment. For men the equation uses the difference between waist and neck circumference plus height; for women it uses the sum of waist and hip circumference minus neck circumference, plus height. Both equations are logarithmic and were published for the US military.
The method depends on measuring accurately. Measure on bare skin or over thin clothing, keep the tape level, and take the measurement as you breathe out. For a more reliable number, measure three times and take the average. If a man's waist is equal to or smaller than his neck, the calculation is not possible.
The BMI estimate by Deurenberg
If you enter weight and age, the calculator also shows a second estimate. The Deurenberg equation from 1991 estimates body fat in adults from BMI, age and sex. It is simple, but it does not separate muscle from fat, so for athletes it can be quite far off.
Two different numbers are not a mistake. The methods measure different things: one uses circumference, the other the relationship between weight and height. To follow progress over time, pick one method and repeat it under the same conditions, for example in the morning, at the same time of day.
Frequently asked questions
What is a typical body fat percentage?
On the ACE scale, the average range is 25–31 % for women and 18–24 % for men. Women naturally have a higher percentage of essential fat than men.
How accurate is the US Navy method?
It is an estimate with a margin of a few percentage points, depending on how accurately you measure. For a more precise result you need a DXA scan or a similar device at a professional.
Why does the calculator ask women for hip circumference?
The equation for women includes the sum of waist and hip circumference, because fat distribution differs between the sexes.
Is the calculator suitable during pregnancy and for teenagers?
No. It is made for adults and does not account for changes during pregnancy, breastfeeding or growth.
How often should I measure?
Body measurements change slowly, so once every two to four weeks is enough, always under the same conditions.
Sources
- Deurenberg P et al. – Body mass index as a measure of body fatness: age- and sex-specific prediction formulas (1991)
- ACE – What are the guidelines for percentage of body fat loss?
- WHO – Obesity and overweight (fact sheet)
Updated: October 2026
For information only, not a substitute for medical advice.