The common murre is 38–46 cm (15–18 in) in length with a 61–73 cm (24–29 in) wingspan.[6] Male and female are indistinguishable in the field and weight ranges between 945 g (2.083 lb) in the south of their range to 1,044 g (2.302 lb) in the north.[7] A weight range of 775–1,250 g (1.709–2.756 lb) has been reported.[8] In breeding plumage, the nominate subspecies (U. a. aalge) is black on the head, back and wings, and has white underparts.