How it's calculated
The US Navy method estimates body fat percentage from circumference measurements — neck and waist for men; neck, waist, and hip for women — combined with height, using a logarithmic regression formula derived from comparison against hydrostatic (underwater) weighing.
Body fat percentage categories
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletic | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Obese range | 25%+ | 32%+ |
Clinical use
- The Navy method is a practical, equipment-free field estimate — useful for tracking change over time, but less precise than DEXA scanning, hydrostatic weighing, or bioelectrical impedance analysis.
- Measurement technique matters: waist is measured at the navel, neck just below the larynx, and hip at the widest point — inconsistent measurement technique between readings is a common source of apparent "change" that isn't real.
- It tends to be less accurate at the extremes of body composition (very lean athletes, or significant obesity) than in the middle of the range.
- Body fat percentage complements, rather than replaces, BMI and waist circumference as ways of thinking about body composition and health risk.
Frequently asked questions
How accurate is the Navy body fat method?
It's a reasonable field estimate that correlates well with more precise methods like hydrostatic weighing in most people, but it can be less accurate at the extremes of body composition (very lean or significantly obese) and depends on careful, consistent measurement technique.
Where exactly should I measure my waist and neck?
Waist is typically measured at the navel, neck just below the larynx (Adam's apple), and — for women — hip at its widest point. Measuring at the same spots each time makes tracking change over time more meaningful.
Why does the formula differ between men and women?
Body fat distribution patterns differ by sex, so the original Navy method derived separate regression equations for men and women against hydrostatic weighing, which is why hip circumference is only used in the female formula.
Is body fat percentage more useful than BMI?
They measure different things — BMI is a simple weight-for-height ratio, while body fat percentage estimates actual composition. Body fat percentage can be more informative for very muscular individuals, where BMI can misleadingly suggest overweight or obesity.
References
- Hodgdon JA, Beckett MB. Prediction of Percent Body Fat for U.S. Navy Men and Women. Naval Health Research Center, 1984.
- American Council on Exercise (ACE). Body Fat Percentage Norms.
- Wang J, et al. Comparisons of body-composition prediction equations. Am J Clin Nutr.