If you traveled back in time 67 million years ago to ancient Montana, you’d be entering the realm of a tyrant: the iconic predator Tyrannosaurus rex. Before you venture into that lost world, though, you might want to know: On average, how close is the nearest T. rex to you?

That might sound like an impossible thing to know—but after crunching through two decades’ worth of T. rex research, a new study provides estimates of the animal’s population density. In all likelihood, a T. rex would be within 15 miles of you, if not much closer.

The new study, published last Thursday in Science, also translates these population densities into estimates for how many T. rex ever lived. On average, researchers