The Lumen Method

This lighting lumens calculator applies the standard lumen method: multiply the recommended illuminance for your room type by the floor area, then divide by the utilization and maintenance factors. The result is the total luminous flux the fixtures must deliver.

Lux, Lumens, and Wattage

Lux measures illuminance — lumens per square meter — so a bigger room needs more lumens for the same brightness. LEDs deliver roughly 100 lumens per watt, so the calculator also estimates total LED wattage and the number of common 800 lm and 1600 lm bulbs.

Tuning the Factors

Dark walls, high ceilings, and dirty fixtures lower the utilization and maintenance factors — the defaults of 0.5 and 0.8 are typical. Light-colored rooms with clean fixtures can raise utilization toward 0.6-0.7 and cut the bulb count.