Projection geometry and placement tool
Projector Screen Size Calculator
Calculate projected image size from throw distance, find projector placement for a target diagonal, measure throw ratio, or fit a 16:9 or custom screen within a wall.
Projector throw formulas
Throw ratio = lens-to-screen distance ÷ projected image width. Therefore, image width = distance ÷ throw ratio and distance = image width × throw ratio.
For aspect ratio a:b, height = width × b ÷ a and diagonal = √(width² + height²). A zoom lens with a throw-ratio range produces the largest image at the minimum ratio and the smallest image at the maximum ratio.
Measure from the lens reference point. Manufacturer specifications determine whether the throw distance is measured from the front element, lens center or another reference. Confirm the installation manual, lens shift, offset, zoom range and clearance before mounting.
Checked examples
| Mode | Inputs | Checked result |
|---|---|---|
| Image size | 10 ft distance, 1.15–1.50 throw, 16:9 | 91.788–119.723 in diagonal |
| Placement | 120 in diagonal, 1.15–1.50 throw, 16:9 | 10.023–13.074 ft lens-to-screen distance |
| Measured ratio | 11 ft distance, 8 ft image width | 1.375:1 throw ratio |
| Wall fit | 10 × 7 ft wall, 0.5 ft margins, 16:9 | 123.914 in diagonal; 10.35–13.5 ft throw distance |
Limits and installation checks
- The screen dimensions describe the projected image, not the outside frame, masking or speaker clearance.
- Throw ratio predicts geometry only. It does not determine brightness, contrast, resolution, focus quality or ambient-light performance.
- Lens shift changes image position without intentionally changing throw ratio; digital keystone can reduce usable resolution and should not replace correct placement.
- Confirm the projector’s exact zoom range, lens offset, ventilation, cable path and mounting tolerances in its current manual.
- For ultra-short-throw projectors, small placement errors can cause large alignment changes; use the manufacturer’s model-specific placement diagram.
- All dimensions and aspect-ratio values must be finite and positive. Margins may be zero but cannot consume the entire wall.