Projector Throw Distance CalculatorFree online other calculator — instant results, no sign-up
Calculate lens-to-screen distance from width and throw ratio.
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About the Projector Throw Distance Calculator
The Projector Throw Distance Calculator estimates the lens-to-screen distance needed for a specified image width and projector throw ratio. Use it to plan projector placement or check whether a proposed screen width fits your available projection distance.
- Image width (m)
- The horizontal width of the projected image in meters, not its diagonal size or the width of the screen frame.
- Throw ratio
- The dimensionless ratio of lens-to-screen distance to projected image width, taken from the projector or lens specifications.
Formula and method
D = W × R; with the default inputs, D = 2.4 m × 1.5 = 3.6 m.
- DRequired lens-to-screen distance in meters.
- WProjected image width in meters.
- RThrow ratio, a dimensionless value equal to D ÷ W.
The calculator multiplies image width by throw ratio to estimate the required projection distance. Since the width is entered in meters and throw ratio has no units, the result is in meters. For the default width of 2.4 m and throw ratio of 1.5, the result is 3.6 m.
Worked example
These are the calculator's starting values and the results it actually produces for them.
Inputs
- Image width2.4 m
- Throw ratio1.5
Results
- Result3.6 m
How to use the Projector Throw Distance Calculator
- 1Measure or choose the horizontal width of the projected image, excluding any screen border.
- 2Enter that width in meters; the default is 2.4.
- 3Find the throw ratio for your projector and lens at the intended zoom setting, then enter it; the default is 1.5.
- 4Read the calculated distance: the default inputs produce 3.6 m from lens to screen.
- 5Check the projector manufacturer's installation diagram and allow space for the projector body, ventilation, and cables before mounting.
Reading your result
The result row gives the estimated lens-to-screen distance in meters for the entered image width and throw ratio. With the default inputs, 3.6 m means the lens should be approximately 3.6 m from the screen to produce a 2.4 m-wide image at a throw ratio of 1.5. This is not the distance from the back of the projector or its mounting bracket.
Limitations
This is a geometric estimate that assumes a valid positive image width and throw ratio and a compatible projector setup. It does not verify focus limits, zoom range, lens compatibility, mounting offsets, brightness, or image quality. Digital zoom, keystone correction, and image cropping can change the usable image width. Manufacturer measurement conventions, particularly for ultra-short-throw projectors, may use a specified reference point rather than an easily accessible lens position; consult the model's installation guide for final placement.
Common questions
Can I enter my screen's diagonal size as the image width?+
No. The calculation requires horizontal image width in meters. If you only know the diagonal, use the screen's aspect ratio to determine its width first, and exclude the frame.
What if my projector lists a throw-ratio range?+
Calculate once with the minimum ratio and once with the maximum ratio, keeping the image width unchanged. These results estimate the nearest and farthest placement distances available through optical zoom, subject to the projector's focus and installation limits.
Does the default result include the depth of the projector?+
No. The 3.6 m result is the estimated lens-to-screen distance. You must separately account for the projector body behind the lens and any required ventilation or cable clearance.
Can I use this calculator for an ultra-short-throw projector?+
The width-times-throw-ratio relationship still provides a nominal projection distance, but it may not match the gap between the projector housing and the wall. Use the manufacturer's placement chart to translate that distance into the required housing position and screen height.
Does the calculator save my information?+
Calculations run in your browser. While signed in, inputs and results are automatically recorded in account history; saving a result creates a separate saved record.
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Results are estimates for informational purposes and are not financial, medical or legal advice.