Outdoor projector window count
Estimate how many façade windows one outdoor holiday projector can cover from throw coverage width for Prince William County homes.
windows_per_projector = floor(coverage_width_ft ÷ (window_width_ft + gap_ft)); projectors = ceil(window_count ÷ windows_per_projector)
When to use
Use this when planning window or façade holiday projections and you want a rough projector count from coverage width — not throw distance alone.
Overlap 10–20% of coverage if you need seamless spooky faces across neighboring windows.
Windows you want filled with projection.
Average clear glass width.
Mullion/wall gap between adjacent windows (edge-to-edge).
Width of usable image at your mount distance.
Blend zone if stitching projectors.
Worked example
Example defaults — Coverage 12 ft with 10% overlap → usable ≈ 10.8 ft.
Each bay ≈ 3 + 2 = 5 ft → floor(10.8÷5)=2 windows per projector.
Six windows → 3 projectors (ceil(6÷2)).
Second example: one input changed
From the defaults (Façade window count = 6; Typical window width (feet) = 3; Gap between window centers (feet) = 2; Projector coverage width (feet) = 12; Overlap % = 10), the calculator shows:
Usable coverage width: 10.8 ft
Windows per projector: 2
Projectors needed: 3
Now raise Façade window count from 6 to 9 and keep the other entries. The result becomes:
Projectors needed: 5
Comparing the two runs tells you how sensitive the answer is to that one measurement. If a small change in it swings the result a lot, measure it twice.
Limits / assumptions
Units: feet and percent.
Assumptions: windows in a horizontal row; similar sizes; coverage measured at the wall.
Not a substitute: lumen/brightness design or neighbor light-trespass rules.
Aim projectors so beams do not blast into bedrooms across the street. Secure outdoor mounts against wind.
FAQ
One window only?
Often one projector per feature window looks sharpest.
Need throw distance?
Use Projection mapping distance for mount distance.
Upper and lower floors?
Treat each floor row separately.
Snowflake laser stakes?
Different tool — snowflake projector spread.