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Height and weight

In comparison to the large, robust head, the body was rather small. Average weight for P. robustus may have been 40 kg (88 lb) for males and 32 kg (71 lb) for females; and for P. boisei 50 kg (110 lb) for males and 34 kg (75 lb) for females. At Swartkrans Cave Members 1 and 2, about 35% of the P. robustus individuals are estimated to have weighed 28 kg (62 lb), 22% about 43 kg (95 lb), and the remaining 43% bigger than the former but less than 54 kg (119 lb). At Member 3, all individuals were about 45 kg (99 lb). Female weight was about the same in contemporaneous H. erectus, but male H. erectus were on average 13 kg (28.7 lb) heavier than P. robustus males. P. robustus sites are oddly dominated by small adults, which could be explained as heightened predation or mortality of the larger males of a group. The largest-known Paranthropus individual was estimated at 54 kg (119 lb).

According to a 1991 study, based on femur length and using the dimensions of modern humans, male and female P. robustus are estimated to have stood on average 132 and 110 cm (4 ft 4 in and 3 ft 7 in), respectively, and P. boisei 137 and 124 cm (4 ft 6 in and 4 ft 1 in). However, the latter estimates are problematic as there were no positively identified male P. boisei femurs at the time. In 2013, a 1.34 Ma male P. boisei partial skeleton was estimated to be at least 156 cm (5 ft 1 in) and 50 kg (110 lb).