If you now the calculations for a given projector and screen please add to this thread and in the future the info can be transferred to the wiki etc...
Hopefully this will help when people are looking for replacement projectors and can't afford a Casio :)
Projector make: Epson
Projector mode: EB-X12
IWB make: Promethean
IWB model: ProActiv 78
Distance from front of lens to board minimum: 2.4m
Distance from front of lens to board maximum: 2.9m