The average length of B. bairdii is 10.3 meters for males and 11.2 meters for females. Calves are about 4.5 meters at birth. They are medium to large sized whales and often grouped with the great whales. They are the largest of the Ziphiidae family. Their bodies are long and cylindrical with a characteristic beak where the lower jaw extends about 10 centimeters beyond the tip of the the upper jaw. Their blow hole is low and wide. Their heads are angled backwards when they breathe so that their front teeth and beaks are visible (Minasian et al. 1984; Watson 1981).

B. bairdii have two pairs of teeth, the first pair protruding 9 centimeters from the extended lower jaw. The second pair is roughly 20 centimeters behind the first and grow to about 5 centimeters. The teeth of the female are slightly smaller than those of the male. B. bairdii are a blueish grey color, often with a brown tinge. Their undersides are usually lighter with three patches of white on the throat, between the flippers, and near the navel and anus. These spots range in size from barely visible to an almost continuous stripe across the belly. Two grooves run along the underside of the jaw in a wishbone shape. Females tend to be lighter in color than males, who often have tooth scars on their beaks. B. bairdii have trangular fins about 30 centimeters tall and set far back on the body (Minasian et al. 1984, Watson 1981).

Average mass: 9000 kg.

Range length: 10.3 to 11.2 m.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: female larger

Average mass: 1.138e+07 g.