British researchers have recalculated the size of the Tyrannosaurus rex dinosaur and found it to be more than two to nearly five tons heavier than its scientifically established weight.

The research team from the Royal Veterinary College outside of London led by John Hutchinson measured five different T. rex skeletons from the Field Museum of Natural History in Chicago to get the new weight. Their findings are published in the open-access journal PLoS ONE.

The current weight of the dinosaur that existed 65 to 67 million years ago or during the Cretaceous Period ranged from 4.5 tons to 6.5 tons but these were based on scale models and extrapolation from other living animals. After 3D modeling or putting flesh on 3D models of the real skeletons using a computer, the researchers found that a full grown T. rex weighs as much as nine tons.

"We estimate they grew as fast as 3,950 pounds (1,790 kilograms) per year during the teenage period of growth, which is more than twice the previous estimate," said Hutchinson, according to the Christian Science Monitor.

Based on the new weight and the different sizes of the skeletons, the researchers also calculated the growth rate of the T. rex. They learned that the dinosaur adds thousands of pounds each year when it was 10 to 14 years old, considered the teenage years for the prehistoric reptile. That meant eating 50 kilograms of meat a day, according to Hutchinson.

Duck-billed dinosaurs, triceratops and smaller creatures made up the T. rex's diet.

The T. rex reaches maturity at age 17 and may have lived up to 35 years, according to the researchers. Juvenile T. rex hunted in packs while the adult ones hunted individually by ambush, they added.