How large should your screen be for a large audience?
We know that in order to determine screen size for a projected image, the distance the farthest members of the audience will be sitting from the screen should be the determining factor. After all, if the screen is bigger, people can see it from further away.
For open spaces, auditoriums and conference rooms the width of the screen should be at least 1/6 the distance of the farthest spectator in the audience.
For example, if the back row of an auditorium is 48 ft. away then the width of the screen should be at least 8 ft. wide. This rule of thumb is for minimum screen size. It is OK to go larger. The important thing is to get a screen that is large enough for the audience in the back row to view comfortably.
However, there are other determining factors, most notably the resolution of the image on the screen.
If people are expected to see tiny figures, graphs, etc., it will be more difficult, and the screen needs to be larger.
So as a rule of thumb, we’d recommend 1/4 the size if possible. So if the convention services person at the hotel wants to put you into a room shaped like a bowling alley, you’d best look for another room, because your people in the rear of the audience will be way too far back.