Lighting Lumens per Room Calculator

About this calculator

Lighting design starts from a target illuminance level in lux appropriate to the room's use — a living room typically needs around 150–300 lux, a kitchen work area 300–500 lux, and a bathroom or hallway less — then multiplies that target by the room's floor area in square meters to get the total lumens required. Dividing total lumens by the output of a single fitting gives the number of fittings needed, and dividing total lumens by the luminous efficacy of modern LEDs (roughly 80–100 lumens per watt) gives the approximate wattage draw.

Homeowners and electricians use this calculation when planning or upgrading room lighting because simply matching old incandescent wattage to new LED fittings badly underestimates or overestimates brightness, since LEDs produce far more lumens per watt — a like-for-like wattage swap from incandescent to LED can leave a room dramatically overlit or, if downsized carelessly, too dim for its intended use.

This calculator takes your room area and target lux level, and returns the total lumens, number of fittings and LED wattage you need.