How Big Was A T-Rex?

When you ask anybody to name one dinosaur, the answer will be T-Rex most of the time. Yes, there were bigger predator dinosaurs than the T-Rex, but no other dinosaur has such a big reputation as the beloved Rex. How big was this bigger-than-life T-Rex?

Based on the over twenty Tyrannosaurus rex fossils found worldwide, scientists and researchers have concluded that the average T-Rex measured 12-feet in height and 40-feet in length. Weighing between 11,000 to 15,500 pounds, with a 5-foot skull, the T-Rex was a big dinosaur.

It’s estimated that there were over 2.5 billion T-Rexs alive at some stage, which gives us hope of finding even more of these dinosaur fossils. Each time we discover a T-Rex fossil, we get to add to the picture of what a T-Rex resembles. We know that it was a big dinosaur that dominated their terrain.

How Big Was A T-Rex?

A Tyrannosaurus rex, or T-Rex as kids like to call them, was one of the biggest carnivores to have ever lived. When Steven Spielberg’s Jurassic Park came out in 1993, it allowed us to “experience” the T-Rex attributes.

The movie made most of us thankful that we never have to worry about running into one as we do with bears, big white sharks, and other wild animals that share the earth with us.

According to the renowned American Museum of Natural History and National Geographic, based on fossil specimens following a scientific method, it is estimated that the T-Rex was this big:

Table 1: Tyrannosaurus Rex Statistics.

Tyrannosaurus Rex (T-Rex)Specifications
Height of a T-Rex12 feet
Length of a T-Rex40 feet
Weight of a T-Rex11,000 to 15,500 pounds
Skull size of a T-Rex5 feet in length
How many teeth did T-Rex have60 Teeth In its Mouth.
How long were T-Rex TeethAverage of 8 inches but
could be up to 12 inches long

Interesting T-Rex Facts

Having captured the imagination of the living, this extinct predator has some unbelievably interesting facts regarding its life cycle, diet, predatory habits, geographical location, etc.

Life Cycle Of The T-Rex

Try to picture a baby T-Rex. In my mind, the picture is of a small vicious ankle snapping T-Rex with extra small forearms. All we have ever seen are bones and adult pictures of the fear-inducing beast.

According to an article published in Business Insider, a baby T-Rex resembled some sort of duckling and was covered in a fluffy layer of feathery fuzz.


How big was a baby T-Rex?

The chances of a baby T-Rex surviving its first year was estimated at 40%, and scientists believe they were the size of a chihuahua when they exited the egg. Like most dinosaurs they needed to grow quickly

Predators, disease, and starvation are the most prominent reasons for not reaching the elusive 1st birthday celebrations. Scientists today are still unsure if T-Rex’s parents cared for their young. Despite what Jurassic Park: Lost World showed you!

Although no T-Rex egg has ever been discovered, it’s believed that they hatch from elongated eggs of about 17 inches long. Researchers came to this conclusion after discovering a tiny tyrannosaur jaw in Horseshoe Canyon in 2018.

They could add the jaw to a small tyrannosaur claw discovered in 1983 in Montana. Both the claw and the jaw were deemed to have been in the embryo stage. Fossils of other tyrannosaur families suggest that they laid twenty eggs at a time.

The T-Rex babies that made it to a year quickly grew into the don’t-mess-with-me predators, picking up an estimated 1,700 pounds every year until they reached full adulthood at age 20.

At the age of 11, the diet of a T-Rex was said to be that of small dinosaurs, and at the age of 22, any and every dinosaur had to watch their back.

Sadly, adulthood only translated to a few extra years of life before passing away. It appears that many died before reaching the ripe old age of 28 years.

T Rex Facts infographic

Did The T-Rex Have Any Enemies?

All apex predators are in some way or form in competition when sharing the same space and food source. We can only speculate about who would win a fight against a T-Rex, as the lack of actual evidence is non-existent.

Dinosaur fans always argue about what dinosaurs could “take” other dinosaurs in a fight, citing size, weight, jaw size, speed, and other characteristics to support their claims.

What we do know for certain – due to teeth marks found on T-Rex bones –is that the Deinosuchus (Gigantic crocodile) can be classified as an enemy, as the evidence of a fight suggests.

Some point to the bigger carnivore dinosaurs of that time, the Giganotosaurus and the  Spinosaurus, as possible enemies and victors in a fight. The fight scene in Jurassic Park 3, where the Spinosaurus snaps the T-Rex’s neck, had many a dinosaur fan in an uproar, some in anger, some in ecstasy.

These two dinosaurs lived on different continents, South America and North Africa, and were about 30 million years apart as well. So we can only speculate on them being an enemy of the T-Rex and who would have won an actual fight.

Where Did The T-Rex Live?

Most of the paleontologists’ T-Rex fossils found to date have been in the American Northwest. If you are a resident of Montana, South Dakota, or Alberta (Canada), you can be sure that a T-Rex roamed in your area millions of years ago.


trex size

Was The T-Rex Fast?

Research suggests that tyrannosaurs may have been more agile and faster than other groups of larger predator dinosaurs.

Before claiming the T-Rex to be the Usain Bolt of the dinosaur world, bear in mind that their estimated top speed is thought to be between 10-17 mph maximum. According to a new study, the walking speed is just under 3 mph.

Yes, we all remember how fast the T-Rex was in Jurassic Park, but special effects make things look better than in real life. You would have won gold if you had a walk-off against the T-Rex in the Olympics.

When Was The First T-Rex Fossil Discovered?

1902 was a great year for Barnum Brown, a.k.a. Mr. Bones. The assistant curator for the Department of Vertebrate Paleontology at the American Museum of Natural History at the time discovered a partial skeleton at Hell Creek, Montana.

The skeleton would become what is known as the holotype specimen – a single specimen appointed as the ambassador of a new species. Barnum and his team would make similar discoveries over the next few years out in the West.

How Did The T-Rex Get Its Name?

As Mr. Brown kept finding these T-Rex fossils, a name for the species was required. The American Museum of Natural History president, Mr. Henry Fairfield Osborn, came up with the name in 1905. Loosely translated, he gave the name Tyrannosaurus rex, which means “tyrant lizard king.”

Why Is The Arms Of A T-Rex So Small?

A paleontologist at UC Berkeley, Kevin Padian, has been hosting a seminar called “The Age of Dinosaurs” directed at the university’s first-year students for more than 20-years. He will be first to admit that nobody knows why their arms were so small and that any hypothesis will be hard to substantiate.

He has, however, published a new thesis on the subject in the “Acta Palaeontologia Polonica.” Padian suggests that the forearms being so small was to protect the T-Rex from “accidental or intentional amputation when a pack of T. rexes descended on a carcass with their massive heads and bone-crushing teeth.”

The Biggest T-Rex Discovered

The biggest T-Rex fossil was discovered in Canada, and according to the American Association for Anatomy, this T-Rex weighed an estimated 19,500 pounds when alive. The fossil was given a pet name “Scotty” and consisted of a skeleton that’s 65% complete.

The fossil consists of a skull, hips and partial ribs, tail, and leg bones. “Scotty” was also deemed the oldest specimen, with an estimated life age of 28-years.

Evidence on Size of The Tyrannosaurus Rex

Tyrannosaurus Rex size estimates have the advantage of being more accurate than a lot of other carnivores due to the amount and the completeness of fossils discovered. This allows paleontologists the ability to accurately reconstruct the wight and length of T-Rex, where the longest dinosaur, Spinosaurus, is only known from destroyed or partial remains.

We have the table below with the 5 most complete Tyrannosaurus rex fossil skeletons and their projected heights weight and other information.

Table 2: Evidence of T-Rex Size and Top 5 most complete Fossils discovered.

Fossil and NameFossil Complete %Length EstimateWeight EstimateNotes
Sue85%12.4 metres (40.7 feet) 8-14 tons – 17500 lbs -30,000lbs (18651 lbs)Discovered in 1990 Sue is one of the largest fully grown Tyrannosaurus fossil ever discovered it is in the field Museum of Natural history in Chicago.
Trix75-80%13 metre. 42 feet6 tonnes fossil weight, 12500 lbs) Also one of the largest known T-rex fossils, is in the Naturalis biodiversity center in Montana found in 2013
Scotty70-75%42 feet – 12-13 metresalmost 20,000 lbs – 9 tonsScotty may be the largest known T-Rex ever found. It is in the T-rex discovery centre in Saskatchewan Found in 1991
Thomas70%34 feet longIn the Natural history museum in Los Angeles. discovered in 2003
Stan65%38 feet (11.7 meters) 6-10.8 tonnes. 12-22,000 lbsWas discovered in 1987 and is held in Buffalo South Dakota. i is in Private hands and was sold for 31 million USD in 2020.
Dueling Dinosaurs98 %Unknown – see notesUnknown See notesin 2006 a et of fossilized remains, was discovered that showed a young T-Rex and a triceratops together. With evidence of fighting. It is 98% complete and has had a checkered history of ownership battles. it is now due to be revealed in 2022 to the public but when it is it will be the most complete fossil of both a Tyrannosaurus Rex and a Triceratops.

When Did The T-Rex Roam The Earth?

The T-Rex lived during the late Cretaceous period. You would have found them doing their thing about 90-66 million years ago.

How Did The T-Rex Eat?

Normally, carnivores use sharp serrated teeth to chop and slice their prey’s meat before swallowing. Not the T-Rex, though; he swallowed the meat whole and in big chunks. his Teeth were not all that sharp, cutting wise, put you would not want to be on the wrong end of that huge biting mouth.

We have a huge selection or articles to answer the common and some less common questions about the Tyrannosaurus Rex here on the site and to make it easier to access we have them in the table below.

How heavy was T-RexDid T-Rex Ever Eat PlantsT-Rex Vs. MammothDid T-Rex have Bad Eyesight
Did T-Rex RoarHow Tall was T-rexDifferences between T-Rex and VelociraptorDid T-Rex Hunt in packs
T-Rex Vs SpinosaurusHow big was a T-Rex BrainCould T-Rex Swim?Did T-Rex have Wings
Did T-Rex Lay EggsClosest living relative to T-RexTriceratops Vs. T RexHow fast could T-Rex run
How big was a T-RexT Rex Facts


We are still discovering more interesting facts about the beloved T-Rex each time somebody finds a fossil. The picture will change as science evolves. In fact most dinosaur facts are subject to change as we learn more, and that is just fine. We change what we know as we learn it. No need to stick to outdated ideas.

For now, we have a chicken-like, chihuahua-sized baby that grows into a terrifying carnivorous predator in a matter of years before dying before the age of 28.

They say the good die young. In this case, the bad also die young, it seems.

We have more Tyrannosaurus Rex Facts here and some answers to the most common questions as well. Don’t forget out coloring and fact sheet pages to download and collect as well!

We also have more on the size of the most famous dinosaurs here.


Similar Posts

Leave a Reply

Your email address will not be published. Required fields are marked *