How the body fat calculator works
This calculator uses the U.S. Navy circumference method, which estimates body fat percentage from your height and a few tape measurements: neck and waist for men, plus hips for women. It is typically within 3–4 percentage points of a DEXA scan, and all you need is a tape measure.
As you type, a 3D body is generated from your measurements, so you can see how your shape relates to your body fat level. In Advanced mode you can add chest, arm, thigh and calf measurements to refine the model, and preview how you might look at a different body fat percentage.
How to measure yourself
- Use a flexible tape measure, snug against the skin without compressing it.
- Neck: just below the larynx (Adam's apple), with the tape sloping slightly down to the front.
- Waist: men at the navel, women at the narrowest point. Stand relaxed and don't pull your stomach in.
- Hips (women): around the widest part of the buttocks.
- Measure at the same time of day, ideally in the morning, and average two or three readings.
Body fat ranges
The American Council on Exercise groups body fat percentages into these ranges:
| Category | Men | Women |
|---|
| Essential | 2–5% | 10–13% |
| Athlete | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Obese | 25%+ | 32%+ |
Frequently asked questions
How accurate is the U.S. Navy method?
For most people it lands within about 3–4 percentage points of a DEXA scan. Accuracy depends mostly on measuring consistently, so use the same tape, spot and time of day each time.
Is my data stored?
No. All calculations run in your browser, and nothing you enter is sent anywhere unless you sign in and choose to save a measurement.
What is a healthy body fat percentage?
For general health, roughly 10–20% for men and 20–30% for women is considered healthy. Very low levels are not sustainable for most people. Ask a doctor for personal advice.
Why is the result different from my smart scale?
Smart scales estimate body fat with bioelectrical impedance, which shifts with hydration and time of day. Tape measurements are usually more consistent, so track trends over time with one method.