Where in the body will you find the cephalic index?

The cephalic index or cranial index is the ratio of the maximum width (biparietal diameter or BPD, side to side) of the head of an organism (human or animal) multiplied by 100 divided by its maximum length (occipitofrontal diameter or OFD, front to back). The index is also used to categorize animals, especially dogs and cats.

The cephalic index was widely used by anthropologists in the early 20th century to categorize human populations, and by Carleton S. Coon (American physical anthropologist) in the 1960s. It is now mainly used to describe individuals' appearances and for estimating the age of fetuses for legal and obstetrical reasons.

The cephalic index was defined by Swedish professor of anatomy Anders Retzius (1796–1860) and first used in physical anthropology to classify ancient human remains found in Europe. The theory became closely associated with the development of racial anthropology in the 19th and early 20th centuries, when prehistorians attempted to use ancient remains to model population movements in terms of racial categories.