Instrument · runs in your browser
Recessed lighting calculator
Any footprint, any target, any ceiling. Nothing is sent to a server and nothing is stored.
—
fixtures
Total lumens—required
Grid—across × deep
Spacing—between fixtures
Wall offset—from end walls
Instrument · what it computesThis is the lumen method, not a rule of thumb
It runs the lumen method — the same calculation a lighting designer starts from — rather than the "one light per 4 square feet" rule that most online calculators use. The difference shows up most in rooms that are unusually tall, unusually long and narrow, or lit for real work.
Every input is named, every loss is taken off explicitly, and the arithmetic is on the method page — including the four places it is weakest and when you should override it.
SOURCE·IES lumen-method recommendations·published recommendations, quoted as ranges·REVIEWED JUL 2026
