The Bullmastiff's a powerful dog, which was originally a cross between the English Mastiff and the Old English Bulldog. Originally bred to find and immobilize poachers, the breed has proven popular as a family pet. Appearance Size Males should be 25 to 27 inches tall (AKC Std.) (63 to 68.5 cm) at the withers and 110 to 130 pounds (50 to 59 kg). Females should be 24 to 26 inches (61 to 66 cm) at the withers, and 100 to 120 pounds (45 to 55 kg). Exceeding these dimensions's discouraged by breeder… (More on Bullmastiff)