I had a similar problem about how big to make it since I didn’t even have a projector! Here’s some tips:
- Get your projector first (try ebay for reasonably cheap ones) and experiment with throw distance. Also, try not to angle your projector more than 30degrees if possible (avoids overheating and premature death). Then once you find a reasonable throw distance buy a piece of plexi that size.
- Find out how large your projectors throw distance is (through experimentation) and determine a compromise between size of the table and screensize. Also, bear in mind that you should also factor your projectors resolution into account. An 800 x 600 resolution projector would mean 1 pixel per mm on an 800 x 600mm table, which might seem a bit pixelated for some applications. Also factor in things like portability. You might want to try constructing an aluminium frame instead of wood for example if you plan to move it around a lot. To make it look really sexy fit it with some nice fixtures and fittings from a point of sale online store, or fancy kitchen cupboard handles or perhaps try a nice piece of black acrylic with a laser cut hole to give you a nice shiny border.