How does Civilization VI determine how many religions may exist in a given game? I've heard two primary theories: first, that the number is calculated based on the number of major civs in the game, and second, that the number is locked to the size of the map.
A forum post about Civ V claims the number was locked to the map size in that game, and it seems many base mechanics have stayed the same from V to VI.
That can't be the only factor, though. I'm playing a game right now on a Tiny map (using the default four civs) where the religion menu says that up to three religions will be allowed. However, I've been accumulating Great Prophet points for a long time, and still haven't gotten a religion. In fact, only one civ has (the one that built Stonehenge). When I check the Great People panel, the Great Prophet column just says "All people of this type have been earned." This is true even after I progress to a new tech era.
The only non-standard thing about my game is that I didn't start in the Ancient Era… I think I picked Classical, instead? I'm guessing this has an effect on the number of religions as well.
An explanation of how the game calculates the number of religions allowed per game is all I'm looking for, but some kind of table or chart would be really great for brownie points.
Best Answer
After a little more research, I still don't have a definitive answer, but here's my semi-educated theory:
Like Civ V, the base number of religions per game is tied to the map size, according to the following distribution:
I got these numbers by actually starting a new game with each of the initial condition combos (playing as Catherine de Medici, starting in the Ancient Era). I beelined for starting a religion and checked the "All Religions (1/n)" button after doing so.
There are exceptions, though. In particular, game era makes a difference. Quoting page 133 of the game manual:
So there's no religion at all in games that start halfway through history. My guess is that this is because the game's Great Prophets all come from three eras: Classical, Medieval and Renaissance. So even if your game still has available religion slots left (like mine), you could miss out on getting to found a religion if you've progressed to a later era or all the Great Prophets from your era have already been generated. (This doesn't work the other way around, though; I was able to generate a Classical Era Great Prophet while still in the Ancient Era, and successfully founded a religion with that unit.)
There's still a hole in this theory: I loaded an earlier save file for my game, when I was still in the Renaissance Era, and the "All individuals of this type [Great Prophet] have already been earned" message was already there.