ToolkitBook
Calculate projection distance or screen size based on throw ratio. Enter your screen size to find mounting distance, or input room dimensions to see maximum screen size. Supports common preset ratios and custom values with metric or imperial units. Home theater builders verify projector compatibility, AV installers check placement options, and enthusiasts optimize viewing angles.
Select a throw ratio, enter your screen size or distance, and click "Calculate" to plan your projector setup. All processing runs locally in your browser.
Throw ratio defines how far a projector must be from the screen to produce a given image width. A ratio of 1.2:1 means the projector must be 1.2 meters away for every 1 meter of screen width. If you want a 2-meter wide image, the projector needs to be 2.4 meters from the screen.
Short Throw (0.4:1 - 1.0:1): Designed for small rooms. Produce large images from close distances, ideal for bedrooms or spaces where the projector sits near the screen. They also reduce shadow interference when someone walks between the projector and screen.
Standard Throw (1.0:1 - 2.0:1): The most common type for home theaters. Offer flexibility in placement while maintaining image quality. Most dedicated home theater projectors fall near 1.2:1.
Long Throw (2.0:1+): Designed for large venues like auditoriums or conference halls. Need significant distance for the same screen size but offer mounting flexibility in long rooms.
Check your projector's specification sheet or manual for the throw ratio. Manufacturers list it as a single number or a range. Zoom lenses produce a range, such as 1.2:1 to 1.6:1. For zoom lenses, enter the ratio corresponding to your planned zoom setting.
The calculator includes four preset buttons for common throw ratios:
1.0:1 Short Throw: For a 100-inch diagonal screen, the projector needs only 2.21 meters distance. Suitable for bedrooms, apartments, or rooms where the projector mounts close to the screen.
1.2:1 Common Home Theater: The default setting representing typical home theater projectors. For a 100-inch screen, expect about 2.65 meters of throw distance. If you are unsure of your projector's specification, this provides a reasonable estimate.
1.5:1 Long Throw: A 100-inch image requires about 3.3 meters. These projectors suit larger rooms or ceiling-mounted installations where distance is not a constraint.
2.0:1 Ultra Long Throw: A 100-inch screen requires 4.4 meters. Typically serve large venues, but some home theater enthusiasts use them in long rooms.
You can also enter a custom throw ratio in the input field. This is useful for projectors with specific ratios not covered by the presets.
Mode 1: Known Screen Size to Distance: Use when you have a target screen size and need to find the required projection distance. Enter the diagonal measurement of your desired screen, select the unit (inches or centimeters), and the calculator shows how far back to place your projector. For example, if you want a 120-inch screen and have a 1.2:1 throw ratio projector, you need approximately 3.18 meters from lens to screen.
Mode 2: Known Distance to Screen Size: Use when room constraints limit where you can place the projector. Enter the available distance from projector to screen, and the calculator shows the maximum screen size. If you have 3 meters of throw distance and a 1.2:1 projector, the maximum screen width is 2.5 meters, translating to about 113 inches diagonal.
Screens are measured diagonally, but throw ratio calculations use width. The calculator handles this conversion automatically for 16:9 aspect ratio screens. For this ratio, screen width equals diagonal multiplied by 0.8716. A 100-inch diagonal screen is 87.16 inches wide.
Most home theater projectors and screens use 16:9 aspect ratio, the same as HDTV. If your screen uses a different aspect ratio like 2.35:1 (cinemascope) or 4:3 (traditional), manual adjustments are needed.
The calculator supports multiple units for convenience. Meters work well for metric users and most room measurements. Feet suit imperial measurements. Centimeters provide precision for small distances. Inches remain the standard for screen sizes, even in metric countries.
Planning a New Home Theater: Before purchasing equipment, measure your room's depth. Subtract seating distance from the back wall to find maximum throw distance. Use Mode 2 to determine the largest screen that fits. A general guideline: seating distance should be 1.5 to 2.5 times the screen diagonal. For a 100-inch screen, sit between 3.8 and 6.3 meters away.
Checking Projector Compatibility: If you already own a projector, use its throw ratio to verify it works in your space. Measure the distance from your planned mounting position to the screen wall. Use Mode 2 to see the maximum screen size.
Zoom Lens Considerations: Many projectors have zoom lenses with variable throw ratios. A projector might range from 1.2:1 to 1.6:1. Use the calculator with both extremes to understand your range of options. Plan for the middle of the range to allow adjustment flexibility after installation.
Measuring from Wrong Point: Throw distance is measured from the projector lens to the screen surface, not from the back of the projector or the mounting bracket. When ceiling mounting, account for the projector's physical depth.
Ignoring Screen Border: Screen size refers to the viewable area, not the frame. A 100-inch screen has a 100-inch diagonal image area. The frame adds several inches. When measuring wall space, account for the frame.
Forgetting Keystone Correction: If you must place the projector off-center vertically or horizontally, keystone correction adjusts the image shape digitally. However, this degrades image quality slightly. Plan for lens-centered alignment whenever possible.
Throw Distance and Brightness: Image brightness decreases as throw distance increases. Light spreads over a larger area, reducing intensity. A projector that produces 1000 lumens on a 100-inch screen might only effectively deliver 500 lumens on a 150-inch screen. When planning large screens, verify your projector has sufficient brightness.
Room Lighting Conditions: Screen size affects perceived image quality in different lighting. Larger screens distribute the same light over more area, appearing dimmer. In rooms with ambient light, a smaller, brighter image often looks better than a larger, dimmer one.