How is it calculated?
Uses the U.S. Navy circumference method — only a tape measure needed. Measure the waist at the navel, the neck below the larynx and (women) the hips at the widest point.
Men: 495 ÷ (1.0324 − 0.19077·log10(waist − neck) + 0.15456·log10(height)) − 450