Navy Body Fat Calculator
Estimate your body fat percentage using the US Navy circumference method, the same formula used by the Department of Defense for military fitness assessments. All you need is a measuring tape and your height, neck, waist, and hip (women) circumferences.
The US Navy body fat formula was developed by Hodgdon and Beckett at the Naval Health Research Center. It uses simple circumference measurements to estimate body fat percentage without expensive equipment like DEXA scans or hydrostatic weighing.
The formulas:
- Men: %BF = 86.010 x log10(waist - neck) - 70.041 x log10(height) + 36.76
- Women: %BF = 163.205 x log10(waist + hip - neck) - 97.684 x log10(height) - 78.387
All measurements are in inches. The formula uses the natural relationship between where your body stores fat (waist, hips) versus lean tissue distribution (neck, height).
How to measure accurately:
- Neck: Measure just below the larynx (Adam's apple), tape sloping slightly downward at the back. Do not flare the neck muscles.
- Waist (men): Measure at the navel level, horizontal all the way around.
- Waist (women): Measure at the narrowest point of the natural waist.
- Hips (women): Measure at the widest point of the buttocks, feet together.
- Take each measurement twice and average them. Measure in the morning before eating.
Accuracy: Studies show the Navy method correlates within 1-3% of underwater weighing for most people. It is less accurate for very lean or very muscular individuals. For a 180 lb person, a 2% error means about 3.6 lb difference in estimated fat mass.
This tool is for educational purposes only and should not replace professional medical advice.