Im tying myself up in knots trying to do some calculations for projector height from ceiling for a Screenplay 4805. Ive pretty much sussed the throw distance I need for the width of screen Im planning on buying (190 cm) using the web based tools but the height is a bit trickier. Im using the method described by theritz here: http://www.avforums.com/forums/showthread.php?t=80073&highlight=projector+height+calculation Using this I get the following figures (all in cm): Constants: 190 = Viewable width of screen i.e. max picture width 107 = Picture height (based on 16:9) 304 = Room height 100 = Floor to eyelevel (when seated on sofa ) 47 = Projector lens height from floor when on coffee table So optimal bottom of picture to floor based on eyelevel being 33% the height of the picture is 64cm (100 (107/3)). This leaves the difference between lens height from floor and base of picture from floor being 17cm (64 47). Next top of picture from floor is 171cm (64 + 107) which makes top of picture from ceiling 133cm (304 171). So adding the difference between lens height and top of picture this gives me a theoretical projector height from ceiling of 150 cm (133 + 17) !!! This would be right in my line of view, not to mention most inconvenient for day to day living, so cant be right. I think where Im going wrong is assuming the 47cm from floor to projector lens. I wont know this until I get the projector home and set it up. Obviously I dont want to go and buy a projector if the ceiling to projector height is going to be 1.5m! Am I going about it the right way or is there another way to do this?