What is projector throw distance?
Throw distance is the distance from the projector lens to the screen image plane. Projector specifications commonly express placement as a throw ratio or a minimum-to-maximum throw-ratio range.
Home & Construction · Projector planning
Projector Throw Distance Calculator
Calculate projector throw distance, possible screen size, required throw ratio, or whether a projector's throw-ratio range fits the placement space you have.
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Buying specification
Calculated result-
Enter measurements to calculate.
Method: throw ratio = lens-to-screen distance ÷ image width. Image width and height are derived from the screen diagonal and aspect ratio.
Projector lensScreen
Throw distance is measured from the projector lens to the image plane at the screen. Confirm the exact convention in the model manual.Projector throw ratio formula
Throw ratio = throw distance ÷ image width. Rearranging the same relationship gives throw distance = image width × throw ratio and image width = throw distance ÷ throw ratio.
How screen diagonal becomes image width
Projector throw ratio uses image width, not screen diagonal. The calculator converts diagonal to width and height from the selected aspect ratio before applying throw-ratio math.
Fixed vs zoom throw ratios
A fixed-ratio projector has one ratio. A zoom lens can have a minimum and maximum ratio, producing a valid placement interval for the same screen size.
Worked example: 100-inch 16:9 screen
A 100-inch 16:9 image is about 87.16 inches wide. With a 1.15–1.50 throw-ratio range, the generic lens-to-screen placement range is about 100.23–130.74 inches, or about 8.35–10.89 feet.
How do I calculate projector screen size from distance?
When distance is fixed, divide it by the projector's throw ratio to get image width. With a zoom range, the maximum ratio produces the smaller image and the minimum ratio produces the larger image.
What throw ratio do I need?
Choose the desired screen size and enter the available lens-to-screen distance. The calculator returns the throw ratio to compare against the projector or lens specification.
How do I check whether a projector fits?
Fit mode compares the projector's valid placement interval with your permitted room interval. It reports the actual overlap rather than only returning yes or no.
What this calculator does not decide
It does not select brightness, screen gain, seating position, lens shift, electrical work, structural mounting, wall clearance, or a specific projector model. Ultra-short-throw and model-specific chassis geometry can require additional manufacturer instructions.
Privacy
The calculation runs in this browser page. The app does not upload measurements, require an account, store the project in a database, or send your inputs to a retailer. Copy, CSV, and Print are initiated locally by you.