Projector Screen Size Calculator

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Projector Screen Size Calculator

Choosing the ideal projector screen size for home theatre, cinema, and workplace can be overwhelming. Before buying a projector, it is crucial to make calculations of the essential dimensions required to save you from inconvenience.

A projector screen size calculator will help you determine the proper screen size by calculating the viewing distance, optimal screen height, ideal throw distance, and optimal brightness.

Getting an ideal projector screen size for your home will depend on the space you intend to use it and your sitting distance from the screen.


How Do I Calculate the Projector Screen Size?

1. Measure the Projector Screen

You should measure the screen length from the top left to the right bottom corner of your screen to get the diagonal.

First, measure the width and then multiply it by the fraction of the aspect ratio to get the height. It would help if you used the Pythagorean theorem to get the diagonal measurement.

Use this formula to get the screen width and height;

Screen Width Formula;

To get the screen width take the aspect ratio width (ARw) times the screen diagonal and divide by the square root of the aspect ratio width (ARw) squared plus the aspect ratio height (ARh) squared.

Screen Height Formula:

To get the screen height, take the aspect ratio height (ARh) times the screen diagonal and divide it with the square root of the aspect ratio width (ARw)  squared plus the aspect ratio squared height (ARh) squared.

2. Calculate the Aspect Ratio

The aspect ratio is the link between the height and width of a rectangular screen display that explains the proportion between the height and the width in a numerical ratio. 

For example, if the aspect ratio is 3:1, the width is three times the height. The most commonly used screen ratio is the 16:9 aspect ratio and the 4:3, respectively.

The fraction of the width determines the aspect ratio to that of the height. Find the one with the more significant inch factor and divide the dimensions.

3. Determine the Throw Ratio

The projector screen size is changeable; hence the images created by the projector are determined by the space between the screen and projector torch.

To get the throw ratio, divide the image’s width by the space between the projector and the screen. The ratio is indicated in the form of decimals.

The more space bounding the screen and projector lens, the more the screen size required. Also, the projector’s poor arrangement can alter the images’ size and quality.

Projectors with a short throw ratio can make larger screens in less space, but the regulating factor is the maximum throw ratio available for a projector in a given room.

Related: Short Throw vs Long Throw Projectors – What’s the Difference?

4. Calculate the Projector Screen Size

To find the accurate screen size, you will need to calculate the following;

  • Start with the throw ratio, which you will get after dividing the screen width by the screen’s distance from the projector.
  • Then calculate the screen diagonal by adding width squared to screen size squared.
  • Calculate the aspect ratio, which is the ratio of the screen width to the ratio of the screen height 
  • The width of the projected image is the length between the projector and the screen multiplied by the throw ratio. 

Factors to Consider When Selecting a Projector Screen Size

When contemplating the size of the projector you need, you should first consider the following elements depending on the purpose of the screen.

The Optimal Screen Height

Before getting a projector, consider the recommended screen size for viewing distance.

  1. The screen should be a sixth of the distance between the screen and the last seat for entertainment videos.
  2. For boardrooms or lecturer rooms, the screen should be at least a quarter of the distance between the screen and the furthest seat in the room.
  3. For HDTV projection, the screen size should be a third of the distance between the screen and the center of the sitting area.

The Optimal Screen Width

It would help if you got the width by calculating the screen’s aspect ratio. In most cases, you determine the width by the screen’s height. 

The most used screen size is between 2.5m-3m diagonal, but it will depend on the size of your room.

The Appropriate Size of the Screen for a Small Space

The sitting distance from the screen will determine your screen size in a small space. Divide the distance between your sitting area and the screen by three to get your screen size. E.g., if you sit at 165 inches from the screen, 165 divided by 3 is 55, so your screen size should be 55 inches

Appropriate Size for Large Venues

To calculate the screen size for significant events, you should first determine the following:

Size of Audience

You should determine the number of people you are expecting. For a crowd of around 100 people, a tripod screen is ideal for you. The tripod screen has an aspect ratio of 16:9 or 4:3, respectively. But if your audience is more extensive than 100, you should consider using a fast fold screen.

Aspect Ratio

You can choose the subject aspect ratio depending on the design you want to showcase. It can either be 16:9 or 4:3. Here is a table to determine to help your projector screen size:

Projector screen size table

Approved audience Screen size for aspect ratio 4:3.

(Height by width) in inches

Screen size for aspect ratio 16:9

(Height by width) in inches

100 6 by 8 5.5 by 10
200 7.5 by 10 7 by 12
300 9 by 12 9 by 16
500 10.5 by 14 11.5 by 24

 Projector Brightness and Screen Gain

Your projector should produce adequate lumens (brightness) to provide a good view of the screen content. The lumens increase as the screen size increase.

You should ensure that your projector and the screen match; not all projectors and screens are compatible. Screen brightness is measured in foot-lamberts or candela per Ft Sq.

To calculate the brightness of your screen, take the lumens times the screen gain divided by the area of the screen in square feet.

Screen gain -this is the ability of your screen to increase or decrease the brightness of the projected image. Some screens are advanced to increase the amount of light reflected the viewers, increasing the brightness.

Recommended brightness for dark rooms should be between 16 and 22-foot-lamberts. In contrast, rooms with medium light should be higher than 22-foot-lamberts. Brightness lower than 12-foot-lamberts is not suitable even for dark rooms.



You should determine if the venue is indoors or outdoors. For an indoor venue, check if the ceiling height is suitable to hold the screen set-up. This should include the bottom side.

It is advisable to pre-survey the event site to ensure the screens are suitable for the event arrangement. If the ceiling is low, you can use smaller screens in the middle and back to ensure the content reaches the entire audience.

Projector Screen Size and Viewing Distance

Calculating the optimal viewing distance between the screen and your sitting area is by diagonally measuring your screen’s size and dividing that size by 0.84.

For example:

Projector screen size( in inches) Optimal viewing distance (in meters)
100 inch 3m
110 inch 3.3m
120 inch 3.6m
130 inch 3.9m
150 inch 4.5m

For smaller rooms, you will need an HDTV set-up:

HDTV screen size (in inches) Approved viewing distance (in meters)
42 inch 1.2m to 1.8m
50 inch 1.5m to 2.3m
55 inch 1.7m to 2.4m
60 inch 1.8m to 2.7m

Projector Screen Size Calculator FAQs

How Far Away Does a Projector Need To Be for a 120-Inch Screen?

A projector should be situated at a distance of 166 inches minimum and a maximum of 181 inches from a screen of 120 inches.

How wide Is a 130-Inch Screen?

A 130-inch screen with an aspect ratio of 4:3 has a width of 113 inches, while that with an aspect ratio of 16:9 has a width of 120 inches.

What Is the Projector Distance for a 150-Inch Screen?

According to the Epson projector screen size calculator, the projection distance of a 150 inches screen should be 174 to 283 inches.


The size of the projector screen size you will need will be determined by the size of your room. In addition, your projector’s position might limit your screen size. If you mount your projector at a fixed position, the screen size will be determined by the zoom length of your projector.

It is advisable to calculate your space before you buy your screen. Those dimensions will help you determine the right size of screen and projector to install. Use the Epson projector screen calculator to help you determine what to choose.

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