Projector Calculator

Q: What screen gain should I pick?

It depends on your room light: 0.8–1.0 grey: dark rooms, deeper black levels. 1.0–1.1 matte white: best color, wide viewing angle, dark room. 1.3+ : rooms with lamps or windows. 2.0+ : ALR or ultra short throw screens only. High gain looks brighter head-on but dims for side seats.

Updated Jul 28, 2026 By Jehan Wadia

Introduction

This projector calculator tells you where to put your projector. Pick your projector model or type in its throw ratio, then enter your screen size. The tool shows the exact throw distance you need. It also gives you the screen width, height, and diagonal.

You can work the other way too. If your projector spot is already set, enter the distance and see how big the picture will be. Switch between feet and meters any time.

The calculator adds a few extra helps. Type in your room depth and it warns you if the setup will not fit. Add the lens offset to learn how high or low the image will land. Set your screen gain to see if the material suits your room light. You also get a top-down diagram, a chart, a size table, and the math steps. If you are still shopping for a display, our Screen Size Calculator and Aspect Ratio Calculator pair well with this tool.

How to use our Projector Throw Distance Calculator

Pick your projector or type its throw ratio, then enter your screen size or your throw distance. The calculator shows how far the projector must sit from the screen, plus the screen width, height, and diagonal, a diagram, a chart, and a full size chart.

Find by Projector Model tab: Use this if you know your projector. It fills in the throw ratio and aspect ratio for you.

Search projector model: Type at least 2 letters of a brand or model, like "HT3550". Click a match in the list to load it.

Projector Brand: Choose your brand from the list. Brands are split into current and discontinued models.

Projector Model: Choose your exact model. The throw ratio, aspect ratio, and lens offset load right away.

Edit throw ratio manually: Click this to unlock the throw ratio boxes and type your own numbers. Click again to put the model specs back.

Manual Entry tab: Use this if your projector is not listed. Type the throw ratio from your spec sheet, or click a quick-fill button for a common lens type. If your spec sheet lists the ratio in an odd form, the Ratio Calculator can simplify it for you.

Units: Pick Imperial (feet and inches) or Metric (meters and centimeters). Your numbers convert when you switch. You can also double-check any hand conversion with our Meters to Feet Calculator, Inches To Cm Calculator, or Feet And Inches Calculator.

Aspect Ratio: Pick your screen shape. 16:9 is normal for home theater and TV shows.

Image Size Measured As: Tell us if your size number is the diagonal, the width, or the height. Diagonal is the most common.

Throw Ratio (min and max): Enter the low and high numbers from your projector's specs. If your lens does not zoom, type the same number twice or leave Max blank.

What should the calculator solve for: Choose Throw Distance if you know your screen size. Choose Image Size if you know how far back the projector will sit.

Throw Distance: Enter how far the lens is from the screen. This box is the answer when you solve for distance.

Image Size: Enter your screen size in inches, feet, cm, or meters. This box is the answer when you solve for size.

Max Available Room Depth: Optional. Enter how much space you really have. We warn you if the setup will not fit. For wall planning, the Square Footage Calculator helps you map out the room.

Preset diagonal screen sizes: Click a button like 100" or 120" to fill the size box fast.

Vertical Lens Offset: Enter the offset percent from your specs. It shows how high or low the image lands compared to the lens.

Screen Gain: Optional. Enter your screen's gain number, like 1.0 for matte white. You get advice on brightness and viewing angle.

Distance and screen size display units: Pick how you want the answers shown, such as feet plus inches, inches, or centimeters.

Calculate, Reset, and Copy Results: Results update as you type, but you can click Calculate any time. Reset clears everything, and Copy Results puts your numbers on the clipboard.

Projector Throw Distance and Screen Size

A projector makes a picture by shining light onto a screen. How big that picture gets depends on how far back the projector sits. Move it closer and the image shrinks. Move it back and the image grows. This tool helps you find the right spot in your room for the screen size you want.

What Is Throw Ratio?

Throw ratio is the one number that ties distance and image size together. It is the throw distance divided by the image width. So a throw ratio of 1.5 means the projector must sit 1.5 feet back for every 1 foot of image width.

The math is simple:

Throw distance = throw ratio × image width
Image width = throw distance ÷ throw ratio

Many projectors have a zoom lens, so they list a range like 1.15–1.50 instead of one number. The low number is the widest zoom, and it puts the projector closest to the screen. The high number is the tightest zoom, and it pushes the projector farther away. Any spot between the two works. If you want to see how much bigger one screen is than another, try the Percent Difference Calculator.

Throw Ratio Types

Ultra short throw (about 0.2–0.4): sits on a table right under the screen.
Short throw (about 0.5–0.9): good for small rooms and classrooms.
Standard throw (about 1.1–2.0): the most common type, mounted on a ceiling or shelf.
Long throw (2.0 and up): used in big rooms and halls.

Aspect Ratio and Screen Shape

Throw ratio uses image width, but screens are usually sold by their diagonal size, like a 100-inch screen. Aspect ratio is the link between the two. It is the shape of the picture. Most home theater projectors and movies use 16:9. Business projectors often use 16:10, older ones use 4:3, and wide movie screens use 2.35:1 or 2.39:1. A 100-inch 16:9 screen is about 87 inches wide and 49 inches tall. The diagonal comes from width and height with the Pythagorean theorem, and you can check pixel density for your source resolution with the PPI Calculator.

Lens Offset

Lens offset tells you how high or low the picture sits compared to the lens. It is given as a percent of the image height. A positive offset means the picture lands above the lens, which is what you want when the projector hangs from a ceiling and is flipped over. If the offset is 0, the middle of the picture lines up with the middle of the lens. Knowing this number keeps you from mounting the projector too high or too low. If you are drilling into joists for a ceiling mount, the Stud Calculator helps you find solid framing.

Screen Gain

Screen gain shows how much light a screen bounces back at you. Plain matte white screens are about 1.0. Grey screens are below 1.0 and make blacks look deeper in a dark room. Screens above 1.3 look brighter head-on, which helps in rooms with lights or windows, but the picture can dim if you sit off to the side.

Check Your Room First

Always measure the space you have before you buy. Compare your room depth to the shortest throw distance the projector needs. If the projector needs more room than you have, you must pick a smaller screen or buy a short throw model. Also leave room for people to walk, and remember to check the ceiling height for a mount. While you plan the rest of the theater, the Subwoofer Box Calculator covers the sound side, and the Electricity Cost Calculator shows what running the gear will add to your power bill.

Formulas used

Aspect-ratio width factor

f=\frac{w}{\sqrt{w^2+h^2}}

Image width from diagonal, height, or width

W=D\times f=H\times\frac{w}{h}

Screen height and diagonal from width

H=W\times\frac{h}{w},\qquad D=\frac{W}{f}

Throw distance from throw ratio and image width

T_{\min}=TR_{\min}\times W,\qquad T_{\max}=TR_{\max}\times W

Image width from throw distance

W_{\max}=\frac{T}{TR_{\min}},\qquad W_{\min}=\frac{T}{TR_{\max}}

Vertical lens offset (image centre and edges relative to lens axis)

\Delta_{centre}=\frac{\text{offset\%}}{100}\times H,\qquad \Delta_{top}=\Delta_{centre}+\frac{H}{2},\qquad \Delta_{bottom}=\Delta_{centre}-\frac{H}{2}

Largest image that fits the available room depth

W_{fit}=\frac{R}{TR_{\min}},\qquad D_{fit}=\frac{W_{fit}}{f}

Unit conversion (values handled in metres)

x_{SI}=x\times k_{unit},\qquad x_{unit}=\frac{x_{SI}}{k_{unit}}

Frequently asked questions

Where do I find my projector's throw ratio?

Look in the manual or on the maker's spec page. It is listed as one number like 1.20 or a range like 1.15–1.50. It may also be called "throw ratio (wide–tele)" or shown as a distance chart. If you cannot find it, use the Manual Entry tab and pick the quick-fill button that matches your lens type.

Why does the calculator give me a range instead of one distance?

Because your projector has a zoom lens. Any spot inside that range gives you the same screen size. The short end is full wide zoom. The long end is full tele zoom. Pick whichever spot fits your room best, then use the zoom ring to fine-tune the picture.

Is the throw distance measured from the lens or the wall?

From the front of the lens to the screen surface. It is not measured from the back of the projector or from the wall behind it. Remember to add the length of the projector body plus a few inches for cables when you plan your shelf or mount.

My throw distance is longer than my room. What can I do?

You have four options:

Choose a smaller screen size.
Buy a short throw or ultra short throw projector.
Move the screen to a longer wall in the room.
Mount the projector on the back wall instead of the ceiling middle.

The room depth warning tells you the largest screen that will still fit your space.

Why did my other input box go blank when I typed a number?

That is on purpose. The calculator can only solve for one thing at a time. When you type a screen size, it clears the distance box and solves for distance. When you type a distance, it clears the size box and solves for size. The chip labels show which box is the input and which is the answer.

Does the throw ratio use screen width or screen diagonal?

Width, always. Screens are sold by diagonal, so the calculator converts your diagonal to width using the aspect ratio first. That is why picking the right aspect ratio matters. A 100-inch 16:9 screen and a 100-inch 4:3 screen have different widths, so they need different throw distances.

How high should I mount my projector?

Use the vertical lens offset result. It tells you how far the image centre sits above or below the lens. A ceiling projector is flipped upside down, so a positive offset pushes the picture down toward the screen. Set the lens height so the offset lands the image on your screen, then use lens shift or small tilt to finish.

Can I just tilt the projector to fix the image height?

Try not to. Tilting makes the picture a trapezoid instead of a rectangle. Keystone correction can square it back up, but it crops pixels and softens the image. It is better to set the right height using the offset number, or use a model with lens shift.

What if my projector is not in the list?

Click the Manual Entry tab and type the throw ratio from your spec sheet. The math is exactly the same. You can also start with a similar model in the list, then click "Edit throw ratio manually" to change the numbers.

What screen gain should I pick?

It depends on your room light:

0.8–1.0 grey: dark rooms, deeper black levels.
1.0–1.1 matte white: best color, wide viewing angle, dark room.
1.3+ : rooms with lamps or windows.
2.0+ : ALR or ultra short throw screens only.

High gain looks brighter head-on but dims for side seats.

Does screen gain change my throw distance?

No. Gain only affects brightness and viewing angle. Distance depends on throw ratio and image width. The gain field just gives you advice about whether your screen material suits your room.

What is the difference between 16:9 and 16:10?

16:9 is the shape of TV shows, streaming, and Blu-ray movies. Most home theater projectors are 16:9. 16:10 is a bit taller and is common on business and classroom projectors made for laptops. Using the wrong one gives you black bars or a wrong-size answer.

Why does the table show two distance columns?

One column is the distance at your minimum throw ratio, the other at your maximum. Together they show the full placement window for each screen size. The green row is the size you entered. The "Fits room?" column checks the shortest distance against your room depth.

Can I use this calculator for an ultra short throw projector?

Yes. UST projectors have throw ratios near 0.2 to 0.4, so they sit only inches from the wall. Pick your model or type the small ratio in Manual Entry. Note that UST placement is very touchy, so also check the maker's own placement chart before you fix the cabinet in place.

Should I match my screen to the projector or the other way around?

Measure your room first. Then find the biggest screen that fits inside your available depth, and buy a projector whose throw range covers that distance. Buying a huge screen before you check the room is the most common mistake.

How do I switch between feet and meters?

Use the Imperial or Metric buttons in the Units section. Your numbers convert automatically. Each field also has its own small unit menu, and the Results section lets you show answers as feet plus inches, decimal feet, inches, cm, or meters.

Are the model throw ratios exact?

They are the maker's nominal specs. Real lenses vary a little from unit to unit, and a few models have several lens options. Always leave a few inches of wiggle room in your mount plan, and confirm the final position with a test image before you drill.

What does the top-down diagram show me?

It is a bird's-eye view of your setup. It shows the projector, the light cone, the screen width, and the throw distance. When your lens zooms, a green outline marks the closest spot the projector can sit. The room depth line on the chart shows your limit.

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