That projector has a zoom lens. So image size depends not only on distance, but also the zoom setting being used. Epson has, I think, a zoom/size/throw table for the 5040. Check their web site and see what document downloads are available for the 5040 specifically. The table is likely printed in the back of the Owner's Manual somewhere. My usual setup is with the projector mounted 15 feet from an 82" wide projection screen. With that setup, the zoom lens can make the image a little larger or smaller, but I don't recall by how much.