About 117 billion people have ever lived.

There are more people on Earth today than ever before — nearly 8 billion, to be exact — which represents a full 7% of all 117 billion people estimated to have ever lived throughout the course of human history. The figure comes from the Population Reference Bureau, which released its first estimate in 1995 and has updated it occasionally in the years since. As with most math on this scale, the calculus wasn’t easy. That’s partly because our knowledge of history is ever-evolving: When the bureau initially calculated the number, modern Homo sapiens were thought to have first appeared around 50,000 BCE, but recent discoveries put the actual date closer to 200,000 BCE.

Three main factors go into the math: how long humans are thought to have been walking the Earth, the average population during different eras, and the number of births per 1,000 people during said eras. As you might imagine, the growth has been astronomical — there were just 5 million humans in 8000 BCE, 300 million in 1 CE, and 450 million in 1200. And while the bureau acknowledges that this is “part science and part art,” even being off by a few billion gives us a ballpark figure to imagine all the people who came before us.

And who shall come after.