Can I make a screen size of X inches in a room size of Y by Z? Windows users, please use the Focal Calculator found on the forums. There's also a Javascript based one for non-Windows users, or those who can't or don't want to download programs. The javascript calculator is available online or as a download.

Please note that for a screen bigger is not always better. Well, maybe if you're one of those people who like to sit in the front row at the IMAX, but most people don't. Please choose a screen size that is reasonable for your room and intended viewing position(s).

I recommend once you get the information from the Focal Calculator that you use masking tape to do a mock-up of the screen, and then sit in your chair and look at it. Also, (particularly for those of you who are using shorter throw projectors) I recommend getting a cardboard box, and putting it the indicated distance from the screen, dead center to it.