I can't seem to find in my core book or bestiary how to calculate a monsters CR if the only have class levels. example evil 12 wizard vampire(which has a +2 to base CR). I know it's an easy one, but i can't find it.
Assuming the base creature has a CR less than 1, then the CR of the creature is equal to the number of class levels it has minus 1. A 12th level human wizard would be CR11.
If the creature has a CR greater than or equal to 1, then the rules change a bit. You have to start dealing with associated and non-associated class levels. You can find the rules on that here in the section titled Adding Class Levels.
Thanks guys. i knew it was easy