Throw ratio is the ratio of the projector-to-screen distance to the screen width. A throw ratio of 1.5:1 means that at 1.5 m from the screen the projector casts an image 1 m wide. Different projectors have different throw ratios, which determine the image size possible at a given distance.

Projector Screen Size Calculator

Q: How do I measure throw distance?

Throw distance is the distance from the projector lens to the screen. For a ceiling-mounted projector, measure from the lens to the screen, not from the projector body to the screen.

Q: How do I choose the right aspect ratio?

The choice mainly depends on your use case: 16:9: best for HD films, TV programs and games; the most common choice. 4:3: best for documents, slides and other office content, as well as some older films and TV programs. 21:9: an ultra-wide ratio suited to panoramic films and immersive gaming, though content compatibility may be poorer.

Q: How do I install a projection screen?

Make sure the screen surface is flat and free of wrinkles. For a fixed-frame screen, use a spirit level to keep it level. Set the height according to the viewing position and the projector height; the bottom of the screen is usually about 1–1.2 m above the floor.

Calculate the screen size that fits your throw distance and throw ratio

Screen size calculation

Distance from projector to screen *

Throw ratio *

Screen aspect ratio

Result

inches (diagonal)

Width

Height

Diagonal length

Screen size visualization

Sample projected content

Aspect ratio: 16:9

Aspect ratio

16:9

Throw ratio

1.00:1

Top view (not to scale)

Projector

Throw distance — m

Screen

Viewing position

Suggested viewing distance — m (THX 36°)

The two distances mean different things: throw distance is lens to image, viewing distance is eye to image. If the actual viewing distance is well below the suggestion, the image is large enough to require scanning left and right. Recommend a screen size from your room →

The figures above are geometric reference values. Actual image size depends on the lens zoom range, keystone correction and mounting position.

To specify a projector or screen, contact us for actual product information and a quotation.

Guide

Enter the throw distance

Measure the straight-line distance (in meters) from the projector lens to the screen position. This is the base parameter for the calculation.

Enter the throw ratio

Throw ratio is a key projector parameter, usually found in the manual or datasheet. It is normally written as "X:1"; enter the numeric part only.

Choose an aspect ratio

Choose the aspect ratio that matches your use. 16:9 is the most common format for HD video and film, 4:3 suits presentations and older video content, and 21:9 offers a wider panoramic experience.

Read the result

After you press "Calculate screen size", the tool shows the calculated screen size (in inches and meters) together with a visualization.

FAQ

What is throw ratio?

How do I measure throw distance?

How do I choose the right aspect ratio?

How do I install a projection screen?

About

This is a free screen size calculator for projector setups. It uses standard geometric formulas to derive a suitable screen size from the throw distance and throw ratio you enter.

Whether you are planning a home cinema or installing a projector in a meeting room or classroom, the tool helps you check the numbers before you commit.