The main factors to consider when deciding on screen size are:

1. The dimensions of the audience area
2. The height of the room
3. The projection format (or formats) to be used

Audience area
The most important aim is to make the screen large enough for those in the rear of the audience to see the subject matter easily, but not so large that those in the front have difficulty in taking in the full width of the image.

Screen height
The height of the screen is the key. The following formulas will help you to calculate the best screen size for maximum legibility in 4:3 format:-

For video; film; slides - Screen height should be at least ONE SIXTH of the distance from screen to the furthest seat.

For computer data, charts eg in conference or lecture rooms: use figure of ONE QUARTER.

For complex graphics eg in command/control centre: use HALF the distance for screen height.

The screen width is then determined by the format chosen.


Ceiling Height
The bottom of the screen should be approximately 102-122cm (3-4ft) above the floor in a room with a level floor and several rows of seats. With only one or two rows of seats, or in a sloping (raked) lecture theatre, the bottom of the screen can be 61-92cm (2-3ft) above the floor. In rooms with a very high ceiling, provision for extra drop may be required when positioning the screen.

Projection Formats
Width to height ratios of the popular formats include:

4:3 Video, slides and most computer outputs

16:9 Widescreen TV/video and HDTV

5:4 High-end data graphics

Remember if 35mm slides are to be used, possibly including vertical (portrait) slides a square (1:1) ratio screen will be needed.

Typical meeting room example

Screen to back row distance: 36ft
Min screen height: 6ft
Screen width: 8ft