Calculating screen size and projection distance made simple

So, you’re thinking about getting a projector and want to know where the projector needs to be to fill the screen or to get a certain size image.  Or you know exactly where you want to install the projector but don’t know how big the image will be at that distance. No problem! 

Introducing the Installation Triangle


If you have any two dimensions on the installation triangle – you can calculate the other one. 

So – taking our UHD40 4K projector as an example.  This has a throw ratio (TR) of 1.2~1.59:1

If we want a 100cm wide screen – we multiple the screen width by the TR = projection distance of 121cm~159cm

If we know where we want to place the projector (ie 121cm back) and want to calculate how large the image would be – we divide the distance by the TR which gives a screen width of between 76.1~100cm (depending on how much you zoom in the image).

If you don’t know exactly what model you need but know your screen size and where the projector needs to be – you can calculate your TR.  This will help you to narrow down which models would fit your room.


But put that calculator away!

Optoma has a brilliant distance calculator on its website that does all the hard work for you! Simply put in one dimension and the calculator will do the rest. 


Where you place the projector is an important part of choosing the right projector

Short throw and ultra-short throw projectors can be positioned very close to the wall and still provide a big image on the screen. The benefits here are no shadows and they tend to be brighter by being closer to the screen or wall.

Normal or standard throw projectors sit further back and tend to mounted on the ceiling and above/behind where you would be seated.



Top Tip

If are thinking of placing your projector on a shelf near to the ceiling – don’t.  You would need to tilt the projector which would distort the image shape.  Install the projector under the shelf rather than above -  ideally with a universal mount.