How screen size is worked out
The size that matters is the height of the picture, not the diagonal. A common rule of thumb sets the image height as a fraction of the distance to the farthest viewer: about a sixth for video calls and presentations, a quarter for detailed content such as spreadsheets and drawings, and an eighth for signage that people glance at. The calculator then picks the smallest standard 16:9 screen that meets it.
These rules are a quick, reliable starting point. For formal design work, AVIXA publishes a display image size standard that sizes screens from the smallest text people need to read.
Questions
What size TV do I need for a meeting room?
Measure from the screen wall to the farthest seat. For video calls and slides the picture should be at least a sixth of that distance tall, so a 5 m room needs about a 65″ to 75″ screen.
Is it better to have one large screen or two?
Two screens let remote participants and shared content appear side by side, which suits medium and large rooms. Small rooms usually work best with one.
How high should a meeting room screen be mounted?
For seated rooms, aim for the centre of the screen near seated eye level, around 1.2 m, while keeping the bottom edge high enough to see over heads at the back.