CALCULATOR
Body Fat Calculator
Estimate body fat from a tape measure using the US Navy method. Get your percentage, category, fat mass, lean mass, and what the number means for your next training block.
US Navy circumference method. Measure relaxed, at the navel for waist. Estimate only, roughly 3-4% margin vs a DEXA scan.
How the US Navy body fat method works
The US Navy circumference method estimates body fat from tape measurements rather than equipment. For men it uses neck, waist and height; for women it adds the hip measurement. The formula was developed for large-scale screening, which is exactly why it is practical: a tape measure costs almost nothing.
Accuracy sits at roughly 3 to 4 percentage points compared with a DEXA scan. That is good enough to track direction over weeks, and not good enough to treat a single reading as fact. Measure relaxed, at the navel for waist, first thing in the morning, and always the same way.
Body fat percentage is a far more useful number than weight alone, because it separates the two things the scale cannot: how much of you is fat and how much is lean tissue.
The US Navy formula
All measurements are in centimetres. The formula works because fat distributes predictably around the waist and hips relative to frame size, which is why it needs no equipment beyond a tape measure.
Body fat 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% |
| Above average | 25% and up | 32% and up |
How measurement methods compare
| Method | Typical error | Cost |
|---|---|---|
| DEXA scan | 1-2% | High, clinic visit |
| Hydrostatic weighing | 2-3% | High, specialist facility |
| Skinfold calipers | 3-4% | Low, needs skill |
| US Navy tape method | 3-4% | Free |
| Bioimpedance scale | 4-8% | Low, hydration sensitive |
Measuring consistently
- Measure first thing in the morning, before eating or drinking.
- Keep the tape level and snug without compressing the skin.
- Waist at the navel, neck just below the larynx, hips at the widest point.
- Take each measurement twice and average them.
- Compare over four to six weeks. Week-to-week noise is larger than real change.
Once you know your body fat percentage it answers a question weight alone cannot: whether to recomp, cut, or run a small surplus. The recomposition calculator uses exactly this number to decide.
Frequently asked questions
How accurate is the Navy body fat formula?
Where exactly do I measure my waist?
What is a healthy body fat percentage?
Why is my body fat different from my smart scale?
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General information, not medical advice. Consult a qualified professional before changing your diet, especially with a medical condition.