How to Calculate Projector Distance

Steve Scott

Updated on

Here’s a couple of handy pieces of advice for setting up you backyard cinema.

First and foremost, how far is too far? In other words, how to calculate the optimal distance between the projector and the screen? This is important because it will affect the quality of the picture.

Too far will get you a too big and dim image, to close and you end up with an overly bright and too small an image. Besides, you have to take into account the convenience factor.

It’s time to do some math. If we take D to be the distance from lens to screen, and W to be the width of the screen, then by dividing the former with the latter, we get the ratio of a projector’s throw.

Ideal Projector Distance

Some Handle Equations for Calculating Distance

D/W = Rt

Think of the Projector’s throw ratio (R) as the π of home cinemas.

So, beginning from this formula, we can derive the two formulas for calculating the distance from the screen and the width of the screen, respectively:

D = Rt * W

W = W/Rt

Now, for our purpose, we need to calculate the distance from the projector’s lens to the screen. All we need is the width of the screen and the projector’s throw ratio. For the former, it’s easy enough. Let’s take a random number and say the screen is 6 feet wide. But how do we find out what the ratio of our projector is? Simply consult your projector’s specs.

projector throw distance
showing the distance of projector from couch

Well, since projectors feature zoom lenses, they will not have a single throw ratio, but a range of throw ratios, so we’ll have to write two equations. For now, we’ll take it to be2 – 2.4:1, as this is the most common range, getting:

D = 2 * 6ft = 12ft and

D = 3 * 6ft = 14.4ft

So, in this case, the optimal distance to place your projector would be anywhere from 12 to 18 feet (3.7 to 5.5 meters).

After you’ve managed to decide in the distance, it’s time to manage the cables. To avoid tripping and being snagged by the cabling, bundle them all together, and then place underneath a length of carpet (for indoors), or you could fashion a box casing.

Naturally, you could go with a very long cable and conduct it all around the perimeter of your backyard, but the longer the cable, the more expensive it gets.

chart for throw distance for projector

In addition, besides throw ratio, you also need to manage the viewing ratio. This would, of course, refer to the distance you and your company need to be from the screen to enjoy the screening. This is important because the image that is projected onto the screen actually consists of tiny colored dots.

If you sit too close to the screen, all you will see are these dots, and you won’t be able to observe the picture as a seamless whole. If, conversely, you sit too far, you will lose that cinema feel and miss out on details.

Still confused? Watch this weird dude with a oversized novelty bowtie show you

In Conclusion

Correctly measuring projector distance will ensure you get the best possible image, every time. Remember, positioning can make or break your overall experience. 

Naturally, you won’t always be able to get the most out of your projector. Sometimes the room measurements will prevent you from placing the projector at the right distance.

However, if the circumstances allow it, always make sure to take full advantage of throw distance and throw ratio. Just bring a tape measure with you, find the right spot and enjoy crisp, stunning visuals.

My name is Steve Scott. Father of 2 and owner of Outdoor Movie HQ. I’ve been involved in the A/V industry for most of my life and built this blog to help people better understand projector technology. Please leave a comment if you have any questions.

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