Throw ratio is the distance from the projector lens to the screen divided by the width of the projected image: throw ratio = distance / image width. A ratio of 2.0 means the projector sits 2 units away from the screen for every 1 unit of image width.

How do I find my projector's throw ratio?

Check the projector's spec sheet or manual under "throw ratio" or "lens specifications." Some manufacturers instead publish a throw distance chart for specific diagonal sizes; if so, divide a listed distance by the matching image width to get the ratio.

Should I enter screen width or screen diagonal?

Throw ratio math uses image width, not diagonal, but this calculator accepts either. Pick "Diagonal" and choose the aspect ratio if that is the number you have, and it converts to width automatically.

What does a range like 1.39-2.09 mean?

That is a zoom lens. 1.39 is the ratio at the widest zoom setting (projector closer to the screen, or a larger image at a fixed distance) and 2.09 is the ratio at full zoom-in (projector farther away, or a smaller image at a fixed distance). Enter both values to see the full usable range.

What is a typical throw ratio range?

Short-throw projectors are usually below about 1.0, standard-throw models fall roughly between 1.2 and 2.5, and long-throw projectors for auditoriums or large venues go higher still.

Projector Throw Distance Calculator

Enter your projector throw ratio and screen size to get the ideal throw distance, or work backward from an available distance to the largest screen that will fit.

What do you know?

Throw ratio (min)

Throw ratio (max) — optional, for a zoom lens

Aspect ratio

Unit

Screen size type

Screen width

Enter your throw ratio and screen size, then click Calculate

Results appear here

Throw Distance

Converted to every unit

Value	in	ft	cm	m

Summary

Throw ratio is the distance from a projector lens to the screen divided by the width of the projected image, so a throw ratio of 1.5 means the projector needs 1.5 feet (or any other unit) of distance for every 1 foot of image width. Short-throw projectors have a ratio below roughly 1.0, standard-throw projectors sit between about 1.2 and 2.5, and long-throw projectors go higher for large venues. Zoom lenses list a range, such as 1.39-2.09, instead of a single fixed ratio. This calculator converts between throw ratio, screen size, and mounting distance in either direction.

How it works

Choose a mode: find the throw distance from a known screen size, or find the screen size from a known distance.
Enter the throw ratio from the projector spec sheet. Add a second value for zoom lenses that list a min-max range.
Pick the aspect ratio of the screen or content, and the unit to work in.
Enter the screen width or diagonal (distance mode), or the available throw distance (screen size mode).
Read the result, shown in inches, feet, centimeters, and meters at once.

Use cases

Confirm a projector will fit in a room before buying it.
Find the largest screen that fits a fixed throw distance in a home theater.
Compare a short-throw and a standard-throw projector for the same room.
Plan projector mounting distance for a classroom or conference room.
Check whether a zoom lens ratio range covers a planned installation.
Convert a manufacturer throw distance chart into a specific room's units.

Frequently Asked Questions

Last updated: 2026-09-09 · Reviewed by Nham Vu