It is unknown whether Spinosaurus was stronger than Tyrannosaurus rex. If length and weight are any indication of strength, Spinosaurus was slightly longer than Tyrannosaurus rex but not necessarily heavier. Sources differ on estimates of the maximum mass of Spinosaurus, which range from 7,400 kg (8.1 tons) to 20,000 kg (22 tons). In contrast, T. rex weighed 4,000 to 7,000 kg (about 9,000 to 15,000 pounds).