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Projector Throw Calculator: Distance, Size and Zoom Range
Calculate projection distance, image size or throw ratio for 16:9, 16:10, 4:3 or 2.35:1. Enter a minimum and maximum throw ratio to see the zoom distance range.
Projector Throw Calculator: Distance, Size and Zoom Range: Uses generic throw geometry to calculate lens-to-screen distance, image width, height and diagonal. Zoom ratios give a range of possible lens positions for the calculated width. It includes no model database, optical offsets or installation clearances; those require your manufacturer's manual. Runs 100% locally in your browser with zero server file uploads.
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Throw ratio = distance / image width. Distance = ratio × width. Width = distance / ratio. Diagonal = width × √(a² + b²) / a for aspect a:b. Zoom distance range = width × minimum ratio to width × maximum ratio.
This is generic geometry, with no brand or lens database. Measure from the lens reference point specified in your manual. Lens shift moves the image vertically or horizontally; it does not change the basic throw-ratio equation. Shift limits, zoom interactions, image offset and ultra-short-throw installation clearances need the manufacturer's diagram. Keystone correction can reduce usable image size.
Physical screen size · Viewing distance · Aspect ratio calculator
Throw geometry
Throw ratio T = distance L / image width W. Therefore L = T × W and W = L/T. Diagonal = W × √(a²+b²)/a for aspect a:b. Zoom distances = W × minimum and maximum throw ratios. These are generic geometric relationships; no brand specifications are bundled.
Lens reference and shift
Manufacturer diagrams show why projection distance and horizontal or vertical shift must be checked for the actual lens. Epson Throw Distance Simulator user manual, used only for measurement definitions: https://files.support.epson.com/pdf/dl_page_linked/epson_tds_usersmanual-revb-eai.pdf . Lens data and diagrams are not reproduced in this calculator.
How to use it
- Choose which quantity to calculate and the image aspect ratio.
- Enter a throw ratio and screen size, or distance and image width.
- Enter the zoom throw-ratio range and check the distances against your lens manual.
Privacy & limitations
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Frequently asked questions
Which distance should I measure?
Use the lens reference point specified in the projector manual, not the rear of the housing. Short-throw layouts can have separate clearance diagrams.
Does lens shift change throw ratio?
Lens shift moves the image sideways or vertically. The basic width-to-distance relationship remains, but practical shift limits and zoom interactions depend on the lens.
Is throw ratio the zoom magnification?
No. Throw ratio is distance divided by image width. A zoom range here needs its minimum and maximum throw ratios, not a single optical zoom multiplier.
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