Astronomer Derrick Pitts says if about a quarter of the people on the planet are children, and maybe half of those children celebrate Christmas, Santa would have to visit about a billion children in a 24 hour period, which works out to about 11,000 children per second.
But that number doesn't take into account bathroom breaks or other pit stops along the way.
"If he sits to eat cookies and milk, that could severely cut his number in half," Pitts said.
Which means he'd have to travel even faster to make it.
"In the time that it might take your brain to think about blinking your eye, Santa will have already come to your home and another 4,000 or 5,000 homes," he said.
And at that speed, Pitts says it's no wonder nobody ever sees Santa.
"Because he has to visit 11,000 children in a second and so that means that he's spending 1/11,000th of a second at your home. That's probably much faster than the capability of the video systems that are available these days to actually catch an image," Pitts explained.