The study was conducted by researchers at Florida State and Oklahoma State Universities. They examined previous research on the bite forces of modern crocodiles and birds, then used that information to simulate the musculature of T-Rex's jaws.
"We didn't go in our study with any preconceived notions or expectations," said FSU professor of biology Gregory Erickson to Newsweek. "Minimally, we expected forces over 6,800 pounds, since I had worked with Stanford engineers as a grad student replicating T-Rex bites on cow bones, and that value was deduced."
"The forces we found are prodigious, enough to sink the teeth several inches into bone and shatter them. That is all they needed to do. Natural selection tends not to grossly overbuild. It is not advantageous to waste resources that could be utilized elsewhere for growth, survival or reproduction."
T-Rex probably cracked the bones of its prey open as easily as you might crack open the bones of a chicken — and it did it for much the same reason you might. Bone marrow is rich in fat and calories.
So what does that number mean, 8,000 pounds of force? Here are a few examples to put it in perspective: a vise would need about 400 pounds of pressure to crush a human skull (exact figures on this are hard to come by for obvious reasons.) If Bruce Lee kicked you in the face, he'd generate around 2,000 pounds of force in the process. Saltwater crocodiles, the world's greatest living biter, can exert around 3,700 pounds with their famous jaws.
So let's say you're walking down the street, minding your own business, when a T-Rex that escaped from Isla Nublar spots you and decides you'd make a tasty snack. It rushes you down at 25 mph and closes its jaw around you. When it bit down, the force would be so crushing that your bones would instantly shatter like they were made of glass and tear you apart. The good news is that the pain, while excruciating, would be very brief.
There were still animals with stronger jaws that the King of the Dinosaurs, but luckily for humans they're all long gone. "We have modeled bite forces for giant fossil crocs at 23,000 pounds, so [T-Rex] was not the king in that regard," Erickson says. "[T-Rex's] tooth pressures, which are more important than bite forces with regard to feeding capacities are however the highest estimated (to date) for any animal."
Erickson was probably referring to the mighty Sarcosuchus imperator ("emperor of flesh crocodiles," which would be a great name for a power metal song), which went extinct over 100 million years ago, was about 40 feet long and wouldn't have even needed to use its teeth — its jaws were big enough to swallow a human whole.
Be glad you don't have to deal with that during your Florida vacation.