English: Derivation of the body roundness index formula by CMG Lee with the silhouette from http://commons.wikimedia.org/wiki/file:anatomical_axes.svg . 1. The subject's height h and waist circumference c are measured. 2. The body is modelled as a cylinder with the same circumference c and height h. 3. The eccentricity e of the largest ellipse (dotted black) that fits in its side view is used in the BRI formula.