What is throw distance
Throw distance is the measurement from the projector lens to the projection screen surface. It determines how large the projected image will be and is one of the most important factors when planning a home theater, conference room, or classroom installation. Every projector has a specific range of throw distances that produce usable, focused images. If the projector is too close, the image will be too small or out of focus; too far, and the image may exceed the screen boundaries or lose brightness. Understanding throw distance helps you select the right projector for your room dimensions or determine exactly where to mount the projector you already own.
Understanding throw ratio
The throw ratio is a single number that defines the relationship between the projector's distance from the screen and the width of the projected image. It is calculated as:
\`\`\` Throw Ratio = Distance / Screen Width \`\`\`
A projector with a throw ratio of 1.5 placed 15 feet from the screen will produce an image that is 10 feet wide. Projectors are typically classified by their throw ratio into four categories:
- **Ultra Short Throw (0.25 - 0.5):** Designed to sit inches from the screen or wall. Ideal for small rooms, interactive whiteboards, and spaces where ceiling mounting is not possible. - **Short Throw (0.5 - 0.8):** Can be placed a few feet from the screen. Popular for classrooms and living rooms with limited space. - **Standard Throw (1.0 - 2.0):** The most common type for home theaters and conference rooms. Requires moderate distance from the screen. - **Long Throw (2.0+):** Used in large venues such as auditoriums, worship spaces, and outdoor screenings where the projector sits far from the screen.
You can find the throw ratio in your projector's specifications sheet. Zoom projectors have a range (e.g., 1.2 - 1.9) rather than a single value.
How to calculate
This calculator uses trigonometry to convert between screen diagonal, screen width, and throw distance based on the aspect ratio and throw ratio.
**From screen size to distance:** \`\`\` Screen Width = Diagonal x cos(atan(Height Ratio / Width Ratio)) Screen Height = Diagonal x sin(atan(Height Ratio / Width Ratio)) Distance = Throw Ratio x Screen Width \`\`\`
**From distance to screen size:** \`\`\` Screen Width = Distance / Throw Ratio Diagonal = Screen Width / cos(atan(Height Ratio / Width Ratio)) Screen Height = Diagonal x sin(atan(Height Ratio / Width Ratio)) \`\`\`
The aspect ratio (such as 16:9 or 4:3) determines the relationship between width and height for any given diagonal measurement. A 100-inch 16:9 screen has a width of about 87.2 inches and height of about 49.0 inches, while a 100-inch 4:3 screen is 80 inches wide and 60 inches tall.
How to use
1. Choose whether you want to calculate **throw distance** (how far to place the projector) or **screen size** (what screen fits your space). 2. Select your measurement units (feet/inches or meters/centimeters). 3. Enter your projector's **throw ratio** from its specification sheet, or use one of the quick presets to estimate. 4. Select the **aspect ratio** that matches your screen (16:9 is standard for most HD and 4K content). 5. Enter either the screen diagonal size in inches or the projector distance, depending on your selected mode. 6. Review the calculated results including the main answer, screen width, screen height, and total screen area.
FAQs
Q: Where do I find my projector's throw ratio? A: The throw ratio is listed in the projector's specifications, usually found in the product manual, on the manufacturer's website, or on the product listing page. It may be listed as a single number (e.g., 1.5) or a range for zoom lens projectors (e.g., 1.2 - 1.9). If a range is given, use the midpoint for an average estimate, or enter the minimum value for the widest image and the maximum for the narrowest.
Q: What throw ratio do I need for a small room? A: For rooms where the projector needs to be within 4 to 6 feet of the screen, look for a short throw projector with a ratio of 0.5 to 0.8. If the projector must sit on a table directly below the screen, an ultra short throw model with a ratio of 0.25 to 0.5 is the best choice.
Q: Does aspect ratio affect the throw distance? A: Yes. For the same diagonal screen size, a wider aspect ratio like 16:9 produces a wider screen, which increases the required throw distance compared to a narrower ratio like 4:3. Always use the correct aspect ratio for your screen when calculating.
Q: Can I use this calculator for rear projection setups? A: Yes. The throw distance calculation is the same whether you are front-projecting or rear-projecting. The distance from the lens to the screen surface remains identical regardless of which side of the screen the projector is on.
Q: What if my projector has a zoom lens? A: Zoom lens projectors have a range of throw ratios. Calculate with both the minimum and maximum values to determine the range of distances (or screen sizes) your projector can achieve. This gives you flexibility in placement.
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