Cephalic index

The cephalic index is the ratio of the maximum breadth of the head to its maximum length, sometimes multiplied by 100 for convenience. It 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.

In adults, the index is no longer used except for describing individuals' appearances, and has no correlation with behavior and very little with place of origin. It is, however, still sometimes used for estimating the age of foetuses for legal and obstetrical reasons, in which case the differences in skull shapes between different populations are still of interest.

Cephalic indices are grouped as

• < 80% : dolichocephalic, or 'long-headed'
• = 80% : mesocephalic, or 'medium-headed'
• > 80% : brachycephalic, or 'short-headed'

Other sources use values between 75% and 81% as the index of mesocephaly. The alternative terms mesocranial and brachycranial are also used.