Projector Throw Distance Calculator

Calculate projector throw distance, required screen width, or throw ratio from any two known values.

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Screen width

Throw ratio e.g. 1.5 means 1.5:1 (throw distance = 1.5× screen width)

Throw distance

3.81 m

12 ft 6 in · 150.0 in

Throw ratio 1.50:1

Screen width 2.54 m / 100.0 in

Throw distance 3.81 m / 12 ft 6 in

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Projectors

Projector throw distance, screen width, and throw ratio

A projector throw distance calculator finds the required distance between a projector lens and the screen for a given screen size, or the maximum screen size a projector can fill from a fixed installation position. Enter any two values — screen width, throw distance, or throw ratio — and calculate the third.

What throw ratio means

Throw ratio is the relationship between the projector's distance from the screen and the width of the image it produces. A throw ratio of 1.5:1 means the projector must be 1.5 times the screen width away to fill that screen. A lower throw ratio — called "short throw" — allows a larger image from a closer distance.

Projectors are classified by their throw ratio into three categories: long throw (ratio > 2.0), standard throw (1.0–2.0), and short throw (0.3–1.0). Ultra-short-throw projectors have ratios below 0.3 and can produce large images from just a few centimetres away.

Throw distance = Screen width × Throw ratio

The fundamental relationship between screen width, throw ratio, and distance.

Screen width = Throw distance / Throw ratio

Rearranged to find the maximum screen width for a fixed room depth.

Throw ratio = Throw distance / Screen width

Used to identify what throw ratio is needed to match a projector to an existing room and screen.

Finding the right projector for your room

Before buying a projector, measure the room depth from where the projector will be placed to the screen wall. Divide that distance by the desired screen width to find the required throw ratio. Then compare that ratio against projector specifications — most product listings state the throw ratio range explicitly.

Remember that the screen width relates to the image width, not the diagonal. For a 16:9 screen, the width is approximately 87% of the diagonal. A 100-inch diagonal 16:9 screen is about 87 inches wide.

Frequently asked questions

What is the throw ratio on my projector?

The throw ratio is listed in the projector's specifications, usually in the manual or on the manufacturer's product page. Variable-zoom projectors list a range (e.g. 1.15:1–1.92:1). The minimum ratio gives the widest image at a given distance; the maximum gives the smallest.

Does screen size refer to diagonal or width?

Throw distance calculations use screen width, not diagonal. Screen sizes are advertised as diagonal measurements. For a 16:9 screen, divide the diagonal by the square root of (1 + (9/16)²) to get the width — or use the screen size calculator on this site to find the exact width from any diagonal and aspect ratio.

What is the difference between short-throw and ultra-short-throw projectors?

Short-throw projectors (ratio 0.3–1.0) produce large images from 1–2 metres away, reducing shadow interference and glare on screen. Ultra-short-throw projectors (ratio < 0.3) sit on a shelf or table directly below or in front of the screen and project upward at a steep angle. They are popular for home cinema where ceiling mounting is not practical.

Projector Throw Distance Calculator

Projector throw distance, screen width, and throw ratio

What throw ratio means

Finding the right projector for your room

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