How to Calculate Body Fat Percentage at Home (Navy Method)
Estimate body fat percentage at home with the US Navy tape method — the formula, a worked example, category ranges, and how accurate it really is.
The US Navy circumference method is the most popular at-home body-fat estimate for a simple reason: it needs a tape measure and about two minutes. It's not as accurate as a DEXA scan, but it's better than pinching your arm and guessing — and it's remarkably consistent when you use the same tape and same landmarks each time.
What you need
- A soft tape measure
- Your height (cm or in)
- Neck circumference (measured just below the larynx, tape angled slightly downward)
- Waist circumference (at navel level for men; at the narrowest point for women)
- Hip circumference (women only — at the widest point)
Stand relaxed, don't suck in, and take each measurement twice.
The formula
Body fat % (US Navy, in inches):
- Men: 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76
- Women: 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387
For metric measurements the formulas are slightly different — the Body Fat Calculator handles both units automatically.
A worked example
A 35-year-old man, 70 in tall, waist 34 in, neck 15.5 in:
- waist − neck = 18.5
- 86.010 × log₁₀(18.5) = 86.010 × 1.267 = 108.98
- 70.041 × log₁₀(70) = 70.041 × 1.845 = 129.22
- Body fat = 108.98 − 129.22 + 36.76 = 16.5%
That puts him in the "fitness" band for men. If his waist grew to 38 in with the same neck and height, the result would rise to about 24% — a good illustration of how sensitive the number is to abdominal circumference.
Category ranges (ACE)
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athlete | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Obese | 25%+ | 32%+ |
Women naturally carry more essential fat than men for reproductive function — the two scales aren't interchangeable.
How accurate is it really?
The Navy method typically comes within ±3–4% of a DEXA scan for average body types, and slightly worse at the extremes (very lean or very heavy). Compared with alternatives:
- DEXA / hydrostatic weighing: the reference standard, ±1–2%, but requires a lab visit.
- Skinfold calipers: ±3% with a trained tester, larger error self-administered.
- Bioelectrical impedance (BIA) scales: ±4–8%, and swings wildly with hydration.
- Navy tape: ±3–4%, but exceptionally repeatable if you measure consistently.
The trend matters more than any single reading. Measure once a week under the same conditions (morning, before eating, same tape tension) and watch the direction over 8–12 weeks.
Why BMI disagrees with body fat
BMI uses only height and weight — it can't tell muscle from fat. A muscular athlete at 15% body fat often reads "overweight" on BMI; a sedentary person at 32% body fat sometimes reads "normal." The Navy method targets the composition question BMI can't answer. For a deeper comparison, see BMI: what it tells you and what it doesn't.
FAQ
How accurate is the US Navy body fat method? Usually within ±3–4% of a DEXA scan for typical body types. Accuracy drops slightly at very low or very high body fat, but repeatability is excellent when measurements are consistent.
Can you calculate body fat percentage without a scale? Yes — the Navy method uses only height and circumference measurements. Your weight isn't in the formula at all.
What's a healthy body fat percentage? For long-term health, most guidelines suggest 10–20% for men and 18–28% for women. Athletic performance ranges are lower, but going below essential-fat levels carries hormonal and immune risks.
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*This is general information, not medical advice — consult a healthcare professional for personal guidance. Estimate your number with the free Body Fat Calculator.*