cephalic index [Gk, kephale, head, index, pointer] , a ratio between the breadth and length of the head. It is calculated as 100 times the maximum breadth of the head, measured at the greatest diameter of the cranial vault above the supramastoid crest, divided by the maximum length measured from the most prominent point on the glabella to the opisthocranion. It is used primarily to estimate fetal age and head shape.
