Body Composition Estimator
Uses the circumference (US Navy) method. Measure the neck below the larynx, the waist at the navel (men) or narrowest point (women), and the hips at the widest point.
Tape-measure methods give a rough estimate only and can differ from clinical methods by several percentage points.
SeafarerFit provides educational information, health calculators, screening tools and medical-examination preparation resources. It does not provide diagnosis, treatment, medical certification or official determination of fitness for sea service.
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Why body composition matters
Two people with the same BMI can have very different amounts of muscle and fat. Tracking an estimate of body-fat percentage alongside your weight helps you see whether training is building muscle or reducing fat.
How to measure
- Use a flexible tape and measure on bare skin, without compressing it.
- Neck: just below the larynx (Adam’s apple), tape sloping slightly down to the front.
- Waist: men at the navel; women at the narrowest point.
- Hips (women): at the widest point of the buttocks.
- Take each measurement twice and use the average.
The circumference method was developed by the US Navy for large-scale screening. It is convenient but less accurate than clinical methods.