An extremely large mammal, it has a head-and-body length of 250 to 330 cm (8.2 to 10.8 ft), not counting a 70 to 105 cm (28 to 41 in) long tail, and is 165 to 220 cm (5.41 to 7.2 ft) high at the shoulder. The average weight is 650 to 1,000 kg (1,400 to 2,200 lb), with an occasional large bull weighing up to 1,500 kg (3,300 lb). Males are about one-fourth larger and heavier than females.
The gaur is a strong and massively built species with a high convex ridge on the forehead between the horns, which bends forward, causing a deep hollow in the profile of the upper part of the head. There is a prominent ridge on the back. The ears are very large; the tail only just reaches the hocks, and in old bulls the hair becomes very thin on the back.
Horns of the gaur grow to a length of 60 to 115 cm (24 to 45 in). Both sexes carry horns, which grow from the sides of the head, curving upwards. They are flattened and regularly curved throughout their length, and are bent inward and slightly backward at their tips. The colour of the horns is some shade of pale green or yellow throughout the greater part of their length, but the tips are black.
A bulging grey-tan ridge connects the horns on the forehead. They present an elliptical cross-section; this characteristic is more strongly marked in bulls than in cows.