World's Fair and International Games

I'm sure this is explained somewhere, but I can't seem to find it. How "long" does it take to complete the world projects like the World's Fair or the International Games? It does not seem to be a set number of turns. My hunch is that there's a certain amount of global hammers that need to be contributed, but where is that number listed? Is it a random amount every game?

In my experience the hammer cost of World's Fair, International Games and ISS seems to be a function of the number of civs in a game. I definitely notice it takes longer on my standard games than it does on duel or tiny.

The amount is fixed, although it depends on the size of the map and the game speed. For standard settings, the World's Fair costs 2800 hammers in all. You can found out how much it is in your game by multiplying the number of civs in the game by the number of hammers required to get silver.

It is written in civilopedia:
350 and 750 hammers per civ
(Per civ at start of the game regarding someone who was eliminated, for standard 8*350 and 8*750)