Skip the reading. here’s the magic formula
Distance = Image Width * Throw Ratio

Thinking of building a projector setup for your home but you’re not too sure if you’ve got the space for a 120″ wide screen? This article will cover how to determine the projection distance needed to project a sizeable image depending on the projector’s specifications.

The Setup

Let’s start off with a projection image that’s 120″ diagonally with a 16:9 format. The same formula can be applied to get the projection distance for any image size or format later on. The projector we’re basing upon is the Epson EH-TW5650, the entry-model for Epson’s home-theatre projectors. Look up the specifications for the EH-TW5650, the number that we’re looking for is the projector’s throw ratio or projection ratio.


The EH-TW5650 has a throw ratio of 1.33-2.16, for now, let’s take it as just 1.33, we’ll get back to why it’s a ranged value. With the desired projected image size and the projector’s throw ratio, we can calculate the projection distance. The formula is as follows:

Distance from screen = Expected Width of Projected Image * Projector’s Throw Ratio

Now substitute in the values for the width of the image and the throw ratio

Distance from screen = 105″ * 1.33

The final value you’ll get is 139.65″ or 3.55m, this is the minimum required distance needed to project a 120″, 16:9 image. There you have it, that’s how you can calculate the projection distance. What’s left now is to measuring your room space and getting the right setup.

Zoom capability

Earlier, when we looked up the throw ratio for the EH-TW5650, we noticed that it had a range value of 1.33-2.16. The reason behind this is that the projector features a zoom capability. This allows you to adjust the size of the image without having to physically move the projector. This feature is helpful for it allows for a more flexible projector placement. It also gives you the choice to either maximise or close the projection distance. We’ll talk more about this in another article.