Body Fat Calculator
Estimate body fat percentage using the US Navy method. Enter waist, neck, and height measurements.
US Navy Body Fat Formula.
Female: BF% = 495 / (1.29579 − 0.35004 × log10(waist+hip−neck) + 0.22100 × log10(height)) − 450
Decoding Your Body Fat Percentage
Body fat percentage is the proportion of your total body mass that consists of adipose (fat) tissue relative to lean mass (muscle, bone, water, and organs). Unlike body weight or BMI, body fat percentage provides a direct measurement of body composition, making it a far more accurate health metric for athletes and fitness enthusiasts. Maintaining a healthy range of body fat is crucial for hormone production, joint cushioning, organ protection, and general metabolic function.
The US Navy Circumference Method Explained
This calculator primarily utilizes the US Navy Circumference Method, a highly reliable and cost-effective algorithm developed to estimate body composition without expensive laboratory equipment. For men, the formula requires height, neck, and waist circumferences. For women, hip circumference is added to account for gynoid fat distribution patterns. The math uses logarithmic equations of these measurements to calculate body density, which is then converted into a fat percentage using the Siri or Brozek formulas.
Interpreting Body Fat Ranges for Health & Performance
Optimal body fat percentages vary significantly by sex and age. For men, essential fat is around 2–5%, while a healthy fitness range is 14–24%. For women, essential fat is higher at 10–13% due to reproductive physiology, and a healthy fitness range is 21–31%. Classifications above these limits (over 25% for men, over 32% for women) represent higher cardiovascular and metabolic risks, making body composition tracking a key tool for long-term preventative health.
Frequently Asked Questions
This calculator uses the U.S. Navy circumference method, which estimates body fat percentage from neck, waist, and hip measurements (plus height). It is one of the most accessible non-invasive methods and correlates well with DEXA scan results for most adults.
According to the American Council on Exercise (ACE): for women, essential fat is 10–13%, athletes 14–20%, fitness 21–24%, acceptable 25–31%, and obese 32%+. For men: essential fat 2–5%, athletes 6–13%, fitness 14–17%, acceptable 18–24%, and obese 25%+.
The Navy method has a margin of error of roughly 3–4%. While DEXA scans and hydrostatic weighing are more precise, they require specialized equipment. The Navy method is sufficiently accurate for general wellness tracking and is used by the U.S. military for fitness assessments.
Measure your neck circumference just below the larynx (Adam’s apple). Measure your waist at the narrowest point (usually around the navel for men, and narrowest point for women). Women also measure hips at the widest point. Use a soft measuring tape and keep it level and snug without compressing skin.
Body fat percentage changes relatively slowly — typically 0.5–1% per month with consistent diet and training. Daily fluctuations in measurements are mostly water retention or tape measurement error. For reliable tracking, re-measure once every 4–6 weeks under consistent conditions.