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Projector Throw Calculator
Use this free projector throw calculator to find exactly where to place your projector. Enter your screen size and your projector's throw ratio, and it works out the minimum and maximum throw distance — the closest and farthest the projector can sit while still filling the screen. Pick a screen preset, or type your own size, and check the room layout diagram to see how the projector, the screen, and the seats fit together.
Find the throw ratio in your projector's manual or specification sheet — it is usually a range like 1.2–2.0. A single number like 1.5:1 means the minimum and maximum are both 1.5.
| Item | Amount |
|---|---|
| Screen width | 104.59 in (8.72 ft) |
| Screen height | 58.83 in (4.90 ft) |
| Minimum throw distance | 10.46 ft |
| Maximum throw distance | 17.43 ft |
| Ideal middle position | 13.95 ft |
How it works
A projector throws its picture across the room, and the size of that picture grows the farther back the projector sits. The relationship is fixed by the throw ratio, a number that belongs to the projector's lens. The throw ratio is simply the throw distance divided by the width of the picture on the screen. A projector with a throw ratio of 1.5 needs to sit 1.5 times the screen width away from the screen: 150 inches back for a 100 inch wide screen, 75 inches back for a 50 inch wide screen. Most home theater projectors have a zoom lens, so the ratio is a range — 1.2 to 2.0, for example — and the projector can sit anywhere inside that range, with zoom filling in the rest.
Minimum throw distance = screen width × minimum throw ratio
Maximum throw distance = screen width × maximum throw ratio
Screens are sold by their diagonal, measured corner to corner, but throw distance depends on the width. The calculator converts the diagonal to a width using the aspect ratio, which is the shape of the picture. A 16:9 screen is the standard widescreen shape used by movies and TV, and its width is about 87 percent of its diagonal: a 120 inch 16:9 screen is 104.59 inches wide and 58.83 inches tall. A 4:3 screen is squarer, so the same 120 inch diagonal gives a wider picture at 96 inches, while a 21:9 ultrawide screen is much wider and shorter. If you already know the width, choose the width option and type it in directly — the aspect ratio then only matters for the height.
The result is a range, not a single number, and that range is your mounting zone. Place the projector anywhere between the minimum and the maximum and the picture fills the screen. The middle of the range is usually the best spot: the lens sits in the middle of its zoom, where the image is sharpest and brightest. The minimum distance matters most in a small room — if the room is shorter than the minimum, the picture will spill off the edges of the screen no matter how you zoom.
Throw ratio also tells you what kind of projector you are looking at. A standard projector has a ratio around 1.2 to 2.0. A short-throw projector has a ratio below 1, often 0.5 to 0.8, and can fill a 100 inch screen from just a few feet away — handy in a small room or a classroom. An ultra-short-throw projector sits almost against the wall, with a ratio around 0.25, and projects upward onto the screen. If you are shopping for a projector, measure your room first, work out the ratio your room allows, and then buy a projector whose range covers it.
Two practical details finish the job. First, the throw distance is measured from the projector's lens, not from the back of the projector or the wall behind it, so leave a few inches for the body of the projector and its cables. Second, the projector should sit level with the center of the screen or use lens shift to line the picture up — tilting the projector and fixing the slant with keystone correction softens the image.
Worked example
You are setting up a home theater with a 120 inch 16:9 screen and a projector whose throw ratio is 1.2 to 2.0.
Step 1: Find the screen width. For a 16:9 screen, width = 120 × 16 ÷ √(16² + 9²) = 120 × 16 ÷ 18.36 = 104.59 inches, which is 8.72 feet.
Step 2: Find the minimum throw distance — 104.59 × 1.2 = 125.51 inches, which is 10.46 feet.
Step 3: Find the maximum throw distance — 104.59 × 2.0 = 209.18 inches, which is 17.43 feet.
Step 4: Find the middle position — (10.46 + 17.43) ÷ 2 = 13.95 feet.
The result is a throw distance of 10.46 – 17.43 ft — the projector can sit anywhere in that range, and 13.95 feet is the ideal middle spot. That is exactly what the calculator shows for these inputs.
FAQ
What is throw distance on a projector?
Throw distance is the distance between the projector lens and the screen that fills the screen exactly with the picture. Every projector has a throw ratio, which is the distance divided by the image width. A projector with a 1.2 to 2.0 throw ratio and a screen 104.6 inches wide can sit anywhere from 10.46 to 17.43 feet away. Move it closer than the minimum and the picture spills off the screen; move it farther than the maximum and the picture no longer fills the screen.
How do I find the throw ratio of my projector?
The throw ratio is printed in the projector's manual and on the manufacturer's specification page, usually written as a range such as 1.2 to 2.0 or a single number such as 1.5:1. It is also often printed on a label near the lens. If you only know the model name, search the manufacturer's site for its specification sheet — the throw ratio is listed under the lens or projection section.
Should I measure the screen by its diagonal or its width?
Either works, because the calculator converts between them. Projectors and screens are sold by diagonal size, so a 120 inch screen means 120 inches measured corner to corner. Throw distance depends on the screen width, though, so the calculator turns the diagonal into a width using the aspect ratio: a 120 inch 16:9 screen is 104.59 inches wide. If you already know the width, choose the width option and type it in directly.
What if my room is too short for the throw distance?
You have three options. First, use a smaller screen, since a narrower screen needs a shorter throw distance. Second, pick a projector with a shorter throw ratio or a short-throw model, which can fill a large screen from just a few feet away. Third, check whether your projector has a zoom lens: zooming out widens the throw range, and the calculator's minimum distance assumes the widest zoom setting.
Does a bigger screen need a longer throw distance?
Yes. Throw distance is the screen width multiplied by the throw ratio, so it grows in direct proportion to the screen. Doubling the screen width doubles the throw distance for the same projector. That is why the first step in planning a home theater is measuring the room, then working backward to the biggest screen that fits the distance you actually have.