Recessed lighting calculator
Any room size, any type, any ceiling. Nothing is sent to a server.
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fixtures
Total lumens—required
Grid—across × deep
Spacing—between fixtures
Wall offset—from end walls
What this actually does
It runs the lumen method — the same calculation a lighting designer starts from — rather than the "one light per 4 square feet" rule of thumb that most online calculators use. The difference matters most in rooms that are unusually tall, unusually long and narrow, or lit for real work.
Everything is explained on the method page, including where the calculation is weakest and when you should ignore it.