Why body fat percentage?
BMI only looks at height and weight and can't tell muscle from fat. A muscular athlete may have a "high" BMI, while someone with little muscle and a lot of belly fat may have a normal one. Your body fat percentage says more about body composition: what share of your weight is fat.
The US Navy method
This calculator uses the method developed by the US Navy to estimate body fat with nothing more than a tape measure. The formula uses the logarithm of your circumference measurements and your height:
- Men: waist and neck, plus height.
- Women: waist, hips and neck, plus height.
The idea is that the waist (and for women the hips) carries much of the body's fat, while the neck reflects overall frame size. Research shows the method agrees reasonably well with more precise measurements across groups, but for an individual it can easily be a few percentage points off.
How to measure
Measure in the morning before eating, with a flexible tape that sits snugly but doesn't dig in. Take each measurement two or three times and use the average.
- Waist: horizontally at the level of the navel, relaxed, after breathing out normally. Don't suck in your stomach.
- Neck: just below the larynx (Adam's apple), with the tape sloping slightly down to the front.
- Hips (women): horizontally at the widest point of the buttocks and hips.
- Height: without shoes, standing straight against a wall.
Worked examples
- A man 5 ft 10 in (70 in) tall with a 34-inch waist and a 15-inch neck comes out at about 17.4%: the "fitness" category. At 175 lb, that is about 30 lb of fat mass.
- A woman 168 cm tall with a 72 cm waist, 32 cm neck and 98 cm hips comes out at about 26.6%: the "average" category.
What is a healthy body fat percentage?
The American Council on Exercise (ACE) uses these categories:
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletes | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| High | 25% and above | 32% and above |
Women naturally carry more body fat than men, partly because of hormones and the reserves needed for pregnancy. Very low body fat is not healthy: essential fat is needed for hormones, organs and the nervous system. For most people body fat rises somewhat with age.
Other ways to measure
- Skinfold calipers, when done properly by a trained person.
- Bioelectrical impedance via a smart scale: convenient but sensitive to hydration and recent meals.
- DEXA scan: accurate but expensive and mainly available in research and specialist clinics.
To track progress, consistency matters more than the absolute number: measure the same way at the same time of day.
Waist size on its own
Your waist measurement is also a useful health indicator by itself. Many health organisations consider a waist above about 40 inches (102 cm) for men or 35 inches (88 cm) for women a sign of increased health risk, because fat around the abdomen is linked to heart disease and type 2 diabetes.
Frequently asked questions
How do I calculate my body fat percentage?
With the US Navy method you only need your height and a few tape measurements. Enter them in the calculator.
How accurate is the US Navy method?
Reasonable for an estimate, but it can be a few percentage points off. It is most useful for tracking changes over time.
What is a healthy body fat percentage for men?
According to ACE, roughly 14 to 24% is fitness to average. 25% and above is in the high range.
What is a healthy body fat percentage for women?
Roughly 21 to 31% is fitness to average. 32% and above is in the high range.
Why does my smart scale give a different number?
Impedance scales measure differently and are affected by hydration. Differences of a few percent are normal.
Is body fat percentage better than BMI?
It says more about body composition. Use both, along with your waist measurement, for a fuller picture.
Last reviewed: 2026-10-06. Results are estimates for information only.