How do you determine what level a character will be when boosted? Is there a formula that goes into it?
For example my Iron man 40 is level 196 and boosted to 324
The problem with your question is that there are a bunch of different kinds of boosts, that apply in different ways.
4* New character boost is always +75 levels. (3* is different, but I forget exactly what it is)
4* PvP-featured character goes from 131->200 (and 70->165)
3* PvP-featured character goes from 131->250 (and 40->145; these two are the reason why I have a bunch of level-131 characters)
Lightning Round-featured is a flat 50% bonus.
4* PvE essential is +90 levels
3* PvE essential is… slightly more than that. +98, maybe?
2* PvE essential is +76
The weekly boosts? I never really tried to work those out, but they definitely aren’t a constant addition, and I don’t think they’re a constant multiplication either. Maybe someone else knows what the formula is.