Body fat percentage
Your fat % with a tape measure: the US Navy method.
- Instant
- Free
- Private (processed locally)
- No sign-up
A tape measure is enough to estimate your body composition
No impedance scale or scanner needed: the US Navy method, developed to assess thousands of recruits quickly, estimates fat percentage from 3 circumference measurements and a validated logarithmic formula. Add your weight and the tool splits fat mass and lean mass in kilos.
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Measure neck and waist
Plus hips for women — in the morning, tape snug not tight.
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Enter the values
The percentage and ACE category appear instantly.
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Add your weight (optional)
To get fat mass and lean mass in kilos.
ACE categories (American Council on Exercise)
| Category | Men | Women |
|---|---|---|
| Essential fat | 2 – 5% | 10 – 13% |
| Athlete | 6 – 13% | 14 – 20% |
| Fitness | 14 – 17% | 21 – 24% |
| Average | 18 – 24% | 25 – 31% |
| High | 25% + | 32% + |
A ±3-4% estimate: useful to track a trend, not for diagnosis. This tool does not replace medical advice or a professional body composition assessment.
Frequently asked questions
How do I take the measurements correctly?
Neck: just below the Adam’s apple, tape slightly sloped forward. Waist: at navel level for men, at the narrowest point for women, without sucking in. Hips (women): at the widest point. Measure in the morning, relaxed, tape snug but not tight.
Is the US Navy method reliable?
It estimates within ±3-4% of reference methods (DEXA, hydrostatic weighing) — enough to track a trend. Its real strength is reproducibility: always measure the same way, and the month-to-month change is very telling.
What body fat percentage should I aim for?
Per ACE: essential fat 2-5% (men) / 10-13% (women), athletes 6-13% / 14-20%, fitness 14-17% / 21-24%, average 18-24% / 25-31%. Going below essential fat is dangerous — it protects organs and hormonal function.
Why is my BMI normal but my body fat high?
That’s the “skinny fat” profile: normal weight, little muscle, abdominal fat. BMI only sees total weight; body fat reveals composition. That is exactly why the two indicators complement each other.