Kitti's hog-nosed bat is about 29 to 33 mm (1.1 to 1.3 in) in length and 2 g (0.071 oz) in mass,[2][3] hence the common name of "bumblebee bat". It is the smallest species of bat and may be the world's smallest mammal, depending on how size is defined. The main competitors for the title are small shrews; in particular, the Etruscan shrew may be lighter at 1.2 to 2.7 g (0.042 to 0.095 oz) but is longer, measuring 36 to 53 mm (1.4 to 2.1 in) from its head to the base of the tail.[4]

The giant golden-crowned flying fox is one of the largest bat species in the world.[11] It is among the heaviest of all bat species, with individuals weighing up to 1.40 kg (3.1 lb). The only bat species known to weigh more than the giant golden-crowned flying fox are the Indian flying fox (Pteropus medius) and great flying fox (Pteropus neohibernicus), with a maximum weight of 1.6 kg (3.5 lb) and 1.45 kg (3.2 lb) respectively.[11][12] It has the longest forearm length of any species, measuring up to 215 mm (8.5 in). The great flying fox has a slightly shorter forearm length, and its wingspan is thus presumed to be lesser as well.[12] The wingspan of the Indian flying fox is up to 1.5 m (4.9 ft),[13] while the giant golden-crowned flying fox has a wingspan of 1.5–1.7 m (4.9–5.6 ft).[11] This species is somewhat dimorphic, with males slightly larger than females in many cranial and external measurements.[14]