The Civilization 6 Culture Victory is not a simple one. At least not on the surface. There's been a great deal of confusion how exactly it works right from the get go with Civ 6 - in fact even with Civ 5 it was something developer Firaxis had to wrestle with.
Thanks to some good old fashioned mathematics from the community however, there is now, at last, enough information to put together a proper guide on how to win the Culture Victory, how to earn Foreign and Domestic Tourists, plus explaining how Tourism works, and how Culture affects it.
We've assembled this guide based on a combination of in-game info, our own testing, and conversations we've held with Firaxis confirming some of the details. It's also worth noting the work done by the community, particularly CivFanatics forum user Victoria, found here. You can also find any of the formula mentioned in the game's .exe files - although we recommend you don't go fiddling around in there unless you know what you're doing!