How To Calculate Projector Screen Size

Are you considering buying a projector, but don’t know what size screen you need? Look no further! This blog post will show you how to calculate projector screen size so you can make an informed decision.

How are projector screens measured?

Projector screens are commonly measured in two ways. The first way is by their diagonal measurement. This is the measurement from one corner of the screen to the opposite corner. The second way projector screens are measured is by their aspect ratio. The aspect ratio is the ratio of the screen’s width to its height. For example, a 4:3 aspect ratio means that for every 4 units of width, there are 3 units of height.

Extrapolating length and width

How To Calculate Projector Screen Size

To determine how big to make your screen, you will need to extrapolate the length and width. The first step is to find the diagonal measurement of your screen. For a standard 16:9 aspect ratio, the width will be 1.78 times the diagonal. To find the height, multiply the width by 0.9. For example, if your screen will have a 120″ diagonal, the width will be 120″ x 1.78 = 213.6″, and the height will be 213.6″ x 0.9 = 191.8″.

What about throw ratio?

How To Calculate Projector Screen Size

Throw ratio is important because it tells you how far away from the screen you need to place your projector in order to get a certain image size. A projector with a low throw ratio, for example, can be placed closer to the screen than one with a high throw ratio.

There are two things that affect a projector’s throw ratio: the lens and the size of the projection chip.

The lens is the piece of glass (or plastic) in front of the projection chip that projects the image onto the screen. The size of the projection chip is pretty self-explanatory—it’s just the physical size of the chip itself.

Projectors with small lenses and large projection chips have low throw ratios, while projectors with large lenses and small projection chips have high throw ratios.

So how do you calculate a projector screen’s size?

It’s actually pretty simple. The formula for calculating a projector screen’s size is:

Screen Width (in inches) = Diagonal Width of Projector Screen (in inches) x 0.84

Screen Height (in inches) = Diagonal Height of Projector Screen (in inches) x 0.84


Now that you know the basics of how to calculate projector screen size, you’re ready to start shopping for your perfect screen. Be sure to keep in mind the projector throw ratio, the screen surface material, and the gain of the screen — all of which will affect your final decision. With a little bit of planning, you’ll be able to find the perfect projection screen for your home theater setup.

Frequently Asked Questions

Do I need a special projector for an outdoor movie screen?

You will need a projector that is weather resistant and can project images in high resolution.

What is the best aspect ratio for an outdoor movie screen?

The standard aspect ratio for movies is 16:9, but you can choose any aspect ratio that you like.

Topline Projector
We're a small team of reviewers and authors who are passionate about projectors. We've been in the business for over 10 years, and we know what it takes to find the topline projector for your needs. We take pride in our work, and we're always looking for ways to improve. We understand that choosing the right projector can be a daunting task. That's why we're here to help.