Work from the seat: choose the image width that fills your field of view comfortably at your actual seating distance, then check the wall can take it and the projector can throw it.
The three constraints, in order
- Seating distance. Too large for the distance means eyes travelling across the picture rather than taking it in.
- The wall. Measure the space between whatever is fixed — a window, a door, a beam. Then measure the screen’s TOTAL width, which on a roller screen is wider than the image by the casing.
- The projector. Throw ratio × image width against the distance available, and brightness against the area.
The 16:9 arithmetic
A 16:9 screen quoted as a diagonal is about 87 % of that in width. A “100 inch” screen is roughly 2.2 m wide and 1.25 m high. Buying by diagonal alone is how a screen ends up overlapping a window frame.
What most people get wrong
They size the screen to the largest image the projector can produce. That is the maximum, not the recommendation — and at maximum size the image is at its dimmest.
Questions people actually ask
Is bigger always better?
No, for two reasons. Light spread over a larger area is dimmer everywhere, so a big image from a modest projector looks washed out. And beyond a certain size relative to the seating distance, the eye has to travel to follow the picture, which is tiring rather than immersive.
What about the black drop above the image?
On roller screens, the black band above the image sets its height on the wall. Makers publish it, and it is what puts the bottom edge at seated eye level rather than at chest height.
Last reviewed 4 September 2026