Fitness
Body Fat % Calculator
Estimate your body fat percentage using only a tape measure and the proven US Navy formula.
How it works
The US Navy method uses circumference measurements to estimate body density and then body fat percentage. For men: BF% = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76. For women, hip circumference is also included. Accuracy is ±3–4% compared to DEXA scanning.
Frequently asked questions
Where do I measure my waist?
Measure at the narrowest point — usually just above the belly button. Exhale normally before measuring.
How accurate is this vs DEXA?
The Navy method has a margin of error of around ±3–4%. DEXA scanning is the gold standard but costs £50–£200 per scan. For tracking trends over time, the Navy method is reliable.