Practical tools for measured work
Projector Throw Distance & Ratio Calculator
Solve lens-to-screen distance, throw ratio or screen diagonal with a scaled optical diagram.
How it works
How to use it: choose the unknown, then enter screen aspect ratio and the other two optical values. Throw distance is measured from the projector lens to the screen plane.
Formula. Throw ratio = lens-to-screen distance / image width. Screen width is derived from diagonal and aspect ratio.
Example. A 120-inch 16:9 screen is about 104.6 inches wide. At 1.20 throw ratio the lens sits about 125.5 inches from the screen.
Current-input example
The result above uses these exact values. This snapshot is included when the page is printed so the output can be checked against the original measurements.
- Solve for
- Throw distance
- Screen diagonal
- 120 in
- Lens-to-screen distance
- 144 in
- Throw ratio
- 1.2
- Aspect width
- 16
- Aspect height
- 9
Primary result: Throw distance: 125.5 in.
Before using the result
- Measure from the datum or reference edge described by this tool, and do not mix inside, outside and centerline dimensions.
- Keep inputs in the displayed units and preserve more precision than the final cutting or purchasing tolerance requires.
- When the result is close to a limit, verify it with a test piece, field measurement, manufacturer drawing or qualified project professional.
Limitations
This is neutral first-order optics. Real projectors have model-specific zoom ranges, lens shift, offsets, focus limits and chassis clearances. Confirm the result inside the chosen projector's official installation manual before mounting.
Frequently asked questions
Why measure from the lens?
Throw ratio describes the optical path from lens to image plane, not distance from the projector's rear panel.
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