The hoary bat is 13 to 14.5 cm (5.1 to 5.7 in) long. It has a wingspan of 40 cm (15.5 in). It weighs 26 g (0.92 oz). Its fur is dense and dark brown, with white tips to the hairs. The body is covered in fur except for the undersides of the wings. Males and females are sexually dimorphic in body mass.