Estimate body fat percentage using the US Navy circumference method — measure neck, waist, and hips to get fat mass, lean mass, and an ACE fitness category.
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Sex
Units
16.5%
Body fat
13.2 kg
Fat mass
66.8 kg
Lean mass
| Body fat percentage | 16.5% |
| Fat mass | 13.2 kg / 29.1 lbs |
| Lean mass | 66.8 kg / 147.3 lbs |
| Category | Fitness |
Also in Body Metrics
Body Composition
The US Navy circumference method estimates body fat percentage from measurements of the neck, waist, and hips — no calipers or lab equipment needed. It was developed by Hodgdon and Beckett in 1984 and remains one of the most widely used field tests for body composition.
The formula uses the natural logarithm of circumference differences to estimate body density, then converts to body fat percentage. For men it needs waist and neck measurements; for women it also needs the hip circumference. The equations differ by sex because fat is distributed differently across the body.
Waist is measured at the navel for men, or at the narrowest point for women. Neck is measured just below the larynx, angled slightly downward. Hips (women only) are measured at the widest point. Take each measurement twice and average them; use a flexible tape pulled snug but not compressing the skin.
Results are classified using ACE (American Council on Exercise) categories: essential fat, athletic, fitness, average, and obese. These are population-level reference ranges, not clinical diagnoses. The Navy method typically has a margin of error of ±3–4 percentage points compared with DEXA scan.
Circumference-based methods work less well for very muscular individuals (they may overestimate fat) and for people with unusual fat distribution. Age, ethnicity, and hydration status can also affect accuracy.
Frequently asked questions
It is generally accurate to within ±3–4% compared to DEXA scan in population studies. Individual accuracy varies based on measurement technique and body type.
For men, measure around the abdomen at the level of the navel. For women, measure at the narrowest point of the torso, usually an inch or two above the navel.
No. A flexible measuring tape is all you need. A second person can help ensure the tape is level and not twisted.
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