Body Fat Calculator (US Navy Method)
The US Navy body fat estimation method uses simple tape measurements to estimate body fat percentage. Developed by the United States Navy for fitness standards assessments, it uses neck circumference, waist circumference (and hip for women), and height in a logarithmic formula. While not as accurate as DEXA or hydrostatic weighing, it requires only a tape measure and correlates reasonably well with these methods. Enter your measurements in centimeters to estimate your body fat percentage and lean body mass.
US Navy body fat formula
Men: BF% = 86.010 × log10(waist - neck) - 70.041 × log10(height) + 36.76
Women: BF% = 163.205 × log10(waist + hip - neck) - 97.684 × log10(height) - 78.387
All measurements in centimeters. Lean body mass (kg) = body weight x (1 - BF%/100). For a male with height = 178 cm, waist = 84 cm, neck = 38 cm: BF% = 86.010 x log10(46) - 70.041 x log10(178) + 36.76 = 86.010 x 1.6628 - 70.041 x 2.2504 + 36.76 = 143.02 - 157.65 + 36.76 = 22.13%.
Body fat classification (approximate)
- Essential fat (men): 2 to 5 percent. Essential fat (women): 10 to 13 percent.
- Athletic (men): 6 to 13 percent. Athletic (women): 14 to 20 percent.
- Fitness (men): 14 to 17 percent. Fitness (women): 21 to 24 percent.
- Acceptable (men): 18 to 24 percent. Acceptable (women): 25 to 31 percent.
- Obesity (men): 25 percent or above. Obesity (women): 32 percent or above.
Body fat calculator: frequently asked questions
What is the US Navy body fat formula?
The US Navy circumference method uses tape measurements to estimate body fat percentage. For men: BF% = 86.010 x log10(waist - neck) - 70.041 x log10(height) + 36.76. For women: BF% = 163.205 x log10(waist + hip - neck) - 97.684 x log10(height) - 78.387. All measurements in centimeters. This formula is used by the US military for fitness assessments.
How accurate is the Navy method?
The Navy method has an error of approximately 3 to 4 percentage points compared to DEXA scanning (the gold standard). It is more accurate than BMI for estimating body composition but less accurate than hydrostatic weighing or DEXA. It is best used for tracking trends over time rather than for absolute body fat values.
How do I take the measurements correctly?
Neck: measure at the narrowest point, below the larynx (Adam's apple). Waist (men): measure at the narrowest point, typically at the navel. Waist (women): measure at the navel. Hips (women only): measure at the widest point around the buttocks. Height: measure without shoes. All measurements should be taken with a non-elastic tape measure. Take two measurements and average them.
What is a healthy body fat percentage?
According to the American Council on Exercise (ACE), healthy body fat ranges are: men 14 to 24 percent (fitness 6 to 13 percent, athletic 6 to 13 percent), women 21 to 31 percent (fitness 14 to 20 percent, athletic 14 to 20 percent). Essential fat is 2 to 5 percent for men and 10 to 13 percent for women.
Does body fat change quickly with training?
Body fat reduction is generally slow: most evidence-based programs produce 0.5 to 1 percent reduction per month with consistent caloric deficit and resistance training. Strength training helps preserve lean mass during fat loss. Rapid weight loss usually includes significant muscle loss, which is counterproductive for strength athletes.
Official sources
- U.S. Navy Physical Readiness Program: US Navy Physical Readiness.
- American Council on Exercise (ACE) body fat classifications: acefitness.org.
- Hodgdon, J.A., & Beckett, M.B. (1984). Prediction of percent body fat for US Navy men from body circumferences and height. Report No. 84-11. Naval Health Research Center.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.