Growing up, getting about and getting dinner
How fast T. rex grew, how fast it moved, what it could see, smell and hear, and what it ate. Some of this scientists agree on. Some of it they are still arguing about.
A teenage growth spurt
T. rex had a growth spurt. Studies suggest young ones stayed under about 1.8 tonnes until about 14 years old, then gained around 600 kg a year for four years. Wikipedia: Tyrannosaurus · checked 24 Oct 2026 Those studies found growth slowed down sharply at about 18 years old. Wikipedia: Tyrannosaurus · checked 24 Oct 2026
A study published in January 2026 argued T. rex grew more gradually than earlier studies said, reaching full size at around 35–40 years. Scientists are still working this out. Wikipedia: Tyrannosaurus · checked 24 Oct 2026
A very young T. rex (a specimen called LACM 28471) is estimated to have weighed only about 30 kg and to have been 2 years old when it died. Wikipedia: Tyrannosaurus · checked 24 Oct 2026 In July 2026, scientists described a foot bone from a hatchling T. rex, estimated at about 75 cm long and 2.5 kg. Wikipedia: Tyrannosaurus · checked 24 Oct 2026
Live fast, die young
More than half of the known T. rex specimens seem to have died within six years of becoming adults. Wikipedia: Tyrannosaurus · checked 24 Oct 2026 Sue was first estimated to be 28 years old when it died. More recent studies put Sue at 27–33. Wikipedia: Tyrannosaurus · checked 24 Oct 2026
Boy or girl?
A T. rex from Montana nicknamed B-rex had medullary bone inside its thigh bone: a special tissue only female birds make when they are about to lay eggs. So B-rex was a female. Wikipedia: Tyrannosaurus B-rex is the only T. rex whose sex has been firmly worked out. Wikipedia: Tyrannosaurus · checked 24 Oct 2026
A 2024 study found little evidence that males and females differed in size. Wikipedia: Tyrannosaurus · checked 24 Oct 2026
How big?
Sue, one of the largest and most complete T. rex skeletons, measured 12.3–12.8 m long and 3.66–3.96 m tall at the hips. Wikipedia: Tyrannosaurus · checked 24 Oct 2026
Recent studies estimate the biggest adults at about 8.4 to 9.2 tonnes. Estimates have varied a lot over the years, from 4.5 tonnes to more than 7.2 tonnes, and most modern estimates fall between 5.4 and 8 tonnes. Wikipedia: Tyrannosaurus · checked 24 Oct 2026
According to most modern estimates, Tyrannosaurus could have grown longer than 13 m, with a hip height of 3.7–4 m. Wikipedia: Tyrannosaurus · checked 24 Oct 2026 Not every adult T. rex was that big. Wikipedia: Tyrannosaurus
How fast?
Estimates of T. rex’s top speed vary a lot: mostly around 9 metres per second (about 32 km/h), but as low as 4.5 m/s and as high as 20 m/s. Wikipedia: Tyrannosaurus · checked 24 Oct 2026
A 2021 study worked out its comfortable walking speed at about 4.6 km/h, close to a human’s. Wikipedia: Tyrannosaurus · checked 24 Oct 2026 One 2017 study suggested an adult T. rex could not run at all, because speeds above about 18 km/h would have broken its leg bones. Wikipedia: Tyrannosaurus · checked 24 Oct 2026
Studies published in 2019 suggest tyrannosaurs could turn more nimbly than other giant theropods of their size. Wikipedia: Tyrannosaurus · checked 24 Oct 2026 A 2020 study found tyrannosaurids were exceptionally efficient walkers. Wikipedia: Tyrannosaurus · checked 24 Oct 2026
Super senses
T. rex had very large olfactory bulbs for its brain size. Of 21 non-avian dinosaurs sampled in one study, it had the best-developed sense of smell. Wikipedia: Tyrannosaurus · checked 24 Oct 2026 T. rex had a very long cochlea, the hearing organ, suggesting it heard low sounds best. Wikipedia: Tyrannosaurus
One study estimated that T. rex had a binocular range of 55 degrees, more than a modern hawk. Wikipedia: Tyrannosaurus · checked 24 Oct 2026 The same study estimated its eyesight was 13 times sharper than a human’s. Other scientists may disagree. Wikipedia: Tyrannosaurus · checked 24 Oct 2026
Estimates of its eye size suggest it saw poorly in low light and hunted during the day. Wikipedia: Tyrannosaurus · checked 24 Oct 2026 For a non-avian dinosaur it had a big brain for its size: among adult non-avian dinosaurs, only some small feathered theropods had relatively bigger ones. Wikipedia: Tyrannosaurus · checked 24 Oct 2026
What was for dinner?
T. rex was by far the largest meat-eater where it lived, and most likely a top predator, hunting duck-billed dinosaurs, horned and armoured dinosaurs, and possibly giant long-necked sauropods. Wikipedia: Tyrannosaurus Was T. rex a hunter or a scavenger? It was one of palaeontology’s longest debates. Most palaeontologists today accept it was a predator that would also scavenge when it could. Wikipedia: Tyrannosaurus · checked 24 Oct 2026
One Edmontosaurus has the tip of a T. rex tooth stuck in its tail bones, with new bone grown around it: it survived the attack. Wikipedia: Tyrannosaurus A Triceratops brow horn and frill bone carry partly healed T. rex tooth marks. The Triceratops survived, but it is not known which animal started the fight. Wikipedia: Tyrannosaurus
Chemical clues in its tooth enamel suggest T. rex sometimes ate dead marine reptiles and fish washed up on the shore of an inland sea. Wikipedia: Tyrannosaurus Bone fragments have been found in fossil poo (coprolites) thought to come from tyrannosaurs. Wikipedia: Tyrannosaurus
T. rex bones with T. rex tooth marks have been put forward as evidence of cannibalism, perhaps scavenging rather than fighting. Wikipedia: Tyrannosaurus
Packs and parents
Did T. rex hunt in packs? Some scientists have suggested it, but the evidence is weak and the idea is not widely accepted. Wikipedia: Tyrannosaurus · checked 24 Oct 2026 There is no direct evidence that T. rex looked after its young. Wikipedia: Tyrannosaurus · checked 24 Oct 2026
Sizes, masses, speeds and bite forces for T. rex are estimates from fossils, and different studies get different answers. Where we give a figure, the source link says which study and the date we checked it.
Next: how it was discovered →