The cranial capacity of the Dmanisi hominins ranges from 546 to 775 cc, with an average of 631 cc. As such, their brain size overlaps with that of H. habilis ( 548–680 cc) and falls below the standard cranial capacity otherwise ascribed to H. erectus and H. ergaster (800–1000 cc). The encephalization quotient (brain-to-body-mass ratio) of the Dmanisi hominins (based on Skulls 1 to 4) is in the range of 2.6–3.1, at the lower end of estimates for H. ergaster/H. erectus and more similar to H. habilis and australopithecines. The encephalization quotient of Skull 5 was estimated at 2.4, within the range of variation for Australopithecus. There are several features that distinguish the Dmanisi hominins from early Homo such as H. habilis, including the well-developed brow ridge, sagittal keels, large orbits, the premolar teeth in the upper jaw having single roots and the angulation of the cranial vault.
