fWHR

Facial width-to-height ratio is the distance between the two cheekbones divided by the height of the upper face, measured from the upper lip to the highest point of the eyelids. That last part is what people most often get wrong when calculating it by hand: it is the upper face, not the whole face, and measuring to the chin instead produces a number about a third smaller that cannot be compared with any published figure. Measured populations centre near 1.9, with most faces between roughly 1.6 and 2.2. fWHR has a genuine research literature, mostly about perceived dominance and about behaviour in competitive settings, and that literature is contested — several larger replication attempts have found much weaker effects than the original studies. It also moves with body composition: fat over the cheeks widens the numerator while the denominator barely changes.