The US Navy Method
This calculator uses the US Navy circumference method to estimate body fat percentage. It is considered one of the most accurate methods that doesn't require specialized equipment like calipers or hydrostatic weighing tanks.
Tips for Accuracy
- Measure the waist horizontally at the level of the navel.
- Measure the neck just below the larynx (Adam's apple).
- Do not pull the tape measure too tight; it should sit on the skin without compressing it.
Why Body Fat Beats the Scale
Two people can weigh exactly the same and share the same BMI, yet one may be lean and muscular while the other carries significantly more fat. Muscle is denser than fat, so someone gaining muscle and losing fat at the same time might see little change on the scale — while their body composition improves dramatically. Body fat percentage captures this "recomposition" that weight and BMI miss entirely.
The Navy Method Formula
Women: %BF = 163.205×log10(waist+hip−neck) − 97.684×log10(height) − 78.387
The formula uses logarithms because the relationship between body circumference and actual body density isn't linear. For most people it lands within 3–4% of a lab-grade DEXA scan — accurate enough to track trends over time, though not for clinical diagnosis.
Healthy Ranges
- Essential fat: roughly 3–5% for men, 10–13% for women (the minimum needed to function).
- Healthy range: around 10–20% for men and 18–28% for women, varying with age and fitness.