How to use the projector calculator
- Choose Distance → screen size when you know the lens-to-screen throw distance. Choose Target width → distance when you know the image width you want.
- Enter the projector’s numeric throw ratio. For example, 1.5 means the distance is 1.5 times the projected image width.
- Enter only the length required by the selected mode. Keep distance and target width in the same unit, then enter a positive custom width:height aspect ratio such as 16:9.
- Calculate to see distance, width, height and diagonal. Editing any field immediately removes the confirmed result and copy state.
Throw-ratio and image formulas
Throw ratio R is defined as throw distance D divided by image width W: R=D/W. Therefore W=D/R in screen-size mode and D=WR in target-width mode.
For aspect ratio x:y, image height is H=W×y/x. The diagonal follows the Pythagorean theorem: d=√(W²+H²).
Calculations retain unrounded values internally and show ordinary results with at most two decimals. Use the same physical unit throughout because the ratio itself has no unit.
Worked examples
3 m distance with a 1.5 throw ratio
In screen-size mode, W=3/1.5=2 m. At 16:9, H=2×9/16=1.13 m and the diagonal is about 2.29 m.
2.4 m target width with a 1.2 throw ratio
In target-width mode, D=2.4×1.2=2.88 m. At 16:9, height is 1.35 m and diagonal is about 2.75 m.
Limits and installation cautions
- This page uses one user-supplied throw ratio, not a zoom range. Check the exact projector manual for minimum and maximum throw ratios.
- Throw distance is normally measured from the lens reference point to the image plane, not from the rear of the case or a ceiling mount. Follow the manufacturer’s definition.
- The result is a geometric image rectangle. It does not account for lens shift, offset, overscan, keystone correction, focus range, brightness or surface obstruction.
- No model search, manufacturer preset, mounting clearance, structural safety or suitability decision is provided. Verify real placement and tolerances before installation.
Frequently asked questions
Is throw ratio based on width or diagonal?
Width. The standard relationship is throw distance divided by projected image width.
Why enter an aspect ratio?
Throw ratio gives image width. The width:height ratio is needed to derive height and diagonal.
Can I enter feet for distance and inches for width?
Not together. Convert both lengths to one unit before using either mode; the output then uses that same unit.