In anthropometry, the cephalic index is an index used originally in attempts to classify race, now used only to describe individuals' appearances and for estimating the age of fetuses. The cephalic index is given by:
(maximum head breadth × 100) / (maximum head length)
People with broad heads (cephalic index over 80) are classed as brachycephalic; those with long heads (less than 76) as dolichocephalic; and those in between as mesocephalic (or mesaticephalic).
In zoology, the index is used to categorize animals, especially cats and dogs.