Estimate your body fat percentage using the US Navy method
Body fat percentage is a more informative measure of body composition than BMI alone, as it distinguishes between fat mass and lean mass (muscle, bone, organs, and water). Two people with the same BMI can have very different body fat percentages and health profiles. The US Navy body fat estimation method uses simple circumference measurements (waist, neck, and hip for women) along with height to estimate body fat percentage. Developed by Hodgdon and Beckett at the Naval Health Research Center, it is one of the most practical and accessible body composition methods, requiring only a flexible tape measure. While not as precise as laboratory methods like DEXA scanning or hydrostatic weighing, the Navy method is accurate to within 3-4% for most people and is widely used in military and clinical settings as a screening tool. It provides a useful estimate for tracking changes over time.
To estimate your body fat percentage: 1. Select your sex. The calculation uses different equations for males and females because fat distribution patterns differ between sexes. 2. Enter your height in centimetres. 3. Measure your waist circumference at the navel (belly button) level while standing relaxed. Do not pull the tape tight or suck in your stomach. Enter the measurement in centimetres. 4. Measure your neck circumference just below the larynx (Adam's apple), with the tape sloping slightly downward at the front. Enter in centimetres. 5. For females: Measure your hip circumference at the widest point of the buttocks. This measurement is required for the female equation. 6. Review your results. The calculator displays your estimated body fat percentage and a category rating based on standard body composition classifications.
The US Navy method uses logarithmic equations with different formulas for males and females: **Male formula:** Body Fat % = 86.010 x log10(waist - neck) - 70.041 x log10(height) + 36.76 **Female formula:** Body Fat % = 163.205 x log10(waist + hip - neck) - 97.684 x log10(height) - 78.387 All measurements are converted from centimetres to inches before applying the formula, as the coefficients were calibrated using inch-based measurements. The formulas work by using the relationship between circumference measurements and subcutaneous fat distribution. A larger waist relative to neck and height indicates higher body fat. For women, hip circumference is included because women store proportionally more fat in the hip and thigh area. Body fat categories differ by sex: - Male: Essential Fat (<6%), Athletes (6-13%), Fitness (14-17%), Average (18-24%), Above Average (25%+) - Female: Essential Fat (<14%), Athletes (14-20%), Fitness (21-24%), Average (25-31%), Above Average (32%+)
The Navy method has limitations: it may be less accurate for very lean or very obese individuals, and for people with unusual body proportions (e.g. very muscular necks). For the most accurate results, take measurements first thing in the morning before eating or drinking. If tracking progress over time, measure at the same time of day under the same conditions. For clinical-grade accuracy, ask your GP about referral for a DEXA scan.