Lighting Calculator

Multiply the room's area (sq ft) by the recommended illuminance for that room type (e.g. ~30 lumens/sq ft for a living room, ~70 for a kitchen), then adjust for ceiling height and wall color.

Divide total lumens needed by the lumens produced per bulb (bulb wattage × LED efficacy, typically 80-100 lumens per watt for modern LEDs).

Light spreads out and loses intensity over distance, so rooms with higher ceilings (over 10 ft) need proportionally more light output to achieve the same illuminance at floor level.

Light-colored walls and ceilings reflect more light back into the room, while dark surfaces absorb it — a room with dark walls needs meaningfully more raw lumens for the same perceived brightness.