Lighting Lux Calculator
Calculate how many light fixtures a room needs to hit a target illuminance.
About this calculator
Rooms lit by guesswork tend to end up under-lit for detailed tasks or over-lit and wasteful for a relaxed living space, because the right number of fixtures depends on matching a target illuminance level, measured in lux, appropriate to the room's use, against the actual light output of your chosen fixtures. This calculator multiplies room area by your target lux level to find total lumens required, then divides that by each fixture's rated lumen output (printed on its packaging or spec sheet) and rounds up to give the number of fixtures needed. Enter room area, a target lux appropriate to the room's function, kitchens and workspaces need more than bedrooms and living rooms, and lumens per fixture, and get a fixture count immediately instead of computing total lumens and dividing by fixture output separately. Because recommended lux levels vary meaningfully by room use and task, checking a reference table for your specific room type before entering a target lux gives a far more useful result than a single generic default.
Worked example
150 sqft living room at 150 lux, 1200 lm fixtures
Result: Fixtures needed ≈ 2
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