TruePurple said:
I see, You mean the larger the map the more cities it allows you before you get corruption? Damn, The whole point for me to want to use Xlarge map is OCN preventing over expansion and allowing for unused landmass latter game.
Well if you guys could point me to a OCN calculator I could use it would be appreciated. I can barely understand that post concening general corruption and OCN short of actually making a calculator myself. (fine I'm stupid, I'm sorry. I need a calculator

)
Twonky's numbers refer to vanilla and PTW.(totally different corruption model here!)
watorry's numbers refer to C3C.
More practically, though, like watorry mentioned, you wouldn't worry too much about these numbers in a game. That is, you would not stop your expansion once you reached a specific number of cities. Just keep gaining more cities. If you run a government
other than communism (or better yet: gov with the "communal" corruption flag, which only applies to communism in a game with default rules), every new city that has a greater distance to the palace than any other city would not affect corruption in these other cities. That's because every city uses a unique rank and the rank is based on palace distance.
If you use communism, every city gets the same (kind of "averaged") rank. That average rank is derived by your total number of cities, no matter where the cities are located. So under communism, every new city would affect rank-based corruption in every other city due to changing that avarage.
Yet again, you wouldn't possibly worry, because communism is usually not your choice for economic reasons in the first place (unit maintenance or high lux-tax due to ww may be indirect economic reasons; btw, increased free unit upkeep is generally a strong point for expanding further under any form of government). So most players switch to communism in case war weariness will be a real issue (i.e. you go for long bloody wars, no emphasis on following a fast tech pace; likely if you go for military victory or maybe domination and still have heaps of conquering to do). After all, a late game revolution from e.g. republic to communism would cost loads of shields and commerce during anarchy.
To sum it up:
You don't stop your expansion because there's rank corruption.

Don't stop, mind.

No. Never ever. Just don't.
And remember, if your core cities grow fast in size and every working tile is improved, you will get a decent amount of
uncorrupted commerce and shields.