Projector Distance Calculator
Work out the throw distance needed for a screen size, or the screen size a room allows.
Last updated · View algorithm, constants and default inputs (JSON)
About this calculator
This first-pass estimate uses throw distance = screen width × the entered throw ratio. Projector zoom ranges, lens offset/shift, mounting clearance and model-specific limits are not included; check the projector maker’s calculator and installation guide before purchase.
Worked example
calculated with the default values below
Throw ratio 1.5 · Desired screen width 100 in · Screen aspect ratio 16:9 widescreen · Available room length 15 ft Throw distance needed 12.50 ft · Screen height 56.2 in · Screen diagonal 114.7 in · Screen area 39.06 sq ft · Widest screen this room allows 120.0 in · Room suitability Yes — with 2.5 ft to spare
General background references
Disclaimer
These calculators give general estimates. Sizing, pricing, availability and standards vary by brand, retailer and country, so treat the output as a starting point and confirm it against the seller's or authority's own figures.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
D = R × W; H = W ÷ a; diag = √(W² + H²); Wmax = (L × 12) ÷ R
- R
- Throw ratio
- W
- Screen width (in)
- a
- Aspect ratio
- H
- Screen height (in)
- D
- Throw distance
- Wmax
- Maximum width fitting the room
- diag
- Diagonal (in)
- L
- Room length (ft)
D = throw ratio × screen width; room-limited width = (room length × 12) ÷ ratio. Assumes a single entered ratio and screen-to-lens distance; zoom, lens offset/shift, mounting clearance and model limits are excluded.
Frequently asked questions
Why does a lower throw ratio let me use a bigger screen in the same room?
The first-pass equation is throw distance = screen width × throw ratio. At 1.5 and a 100-inch-wide screen, that is 150 inches. Actual placement depends on the projector lens, zoom range, offset/shift and mounting clearance, so check the model-specific guide.