Body Fat Calculator
Estimate body fat percentage from height, neck, waist (and hip) measurements with the U.S. Navy circumference method — formula shown, limitations stated plainly. Informational only, not medical advice.
| Category | Body fat |
|---|---|
| Essential fat | 2–5% |
| Athletes | 6–13% |
| Fitness | 14–17% |
| Average | 18–24% |
| Obese | 25%+ |
How to use this tool
- Choose US or metric units and your sex (the Navy equations differ).
- Measure with a flexible tape: neck just below the larynx, waist at the navel — and for the female equation, hips at the widest point.
- Read the estimated body fat percentage and where it falls among common category ranges.
How it works
This is the U.S. Navy circumference method (Hodgdon & Beckett, 1984), which estimates body density from height and tape measurements, converted to percent body fat. Men: 495 ÷ (1.0324 − 0.19077·log₁₀(waist − neck) + 0.15456·log₁₀(height)) − 450, with all measurements in centimeters; the female equation adds hip circumference.
Honest limitations: a tape-measure estimate is typically within ±3–4% of lab methods like DEXA for most people, and less accurate at the extremes of leanness or size. Measure at the same time of day, un-flexed, and track the trend rather than fixating on a single number. This is informational only — not medical advice or a clinical assessment.
Sources & references
Content last reviewed: July 2026.
Frequently asked questions
How accurate is the tape-measure method?
Studies put the Navy method within roughly ±3–4% of laboratory body-composition methods for most adults. It's excellent for tracking change over time; it's not a diagnostic instrument.
What's a healthy body fat percentage?
Commonly cited fitness ranges: roughly 14–24% for men and 21–31% for women counts as average-to-fit, with athletes lower. Healthy varies by age and individual — discuss your own numbers with a healthcare professional.
Why does the female equation include hips?
The Navy equations were fitted separately by sex because fat distribution differs; the hip measurement made the female equation significantly more accurate in the original research.
Where exactly do I measure?
Neck: just below the larynx, tape sloping slightly down at the front. Waist: at the navel for men, at the narrowest point for women. Hips: at the widest point. Snug but not compressing the skin.