Lighting Calculator: Lumens, Watts and Fixtures for Any Room

Your details

Width of the room at floor level.
m
Length of the room at floor level.
m
Ceiling height above the floor. Affects how efficiently fixtures illuminate the work plane.
m
The IES-recommended illuminance level depends on the room type and its primary use.
Task areas need higher illuminance than general ambient lighting.
Dark surfaces absorb light and require a higher lumen output to reach the same illuminance.
Rooms with good natural daylight need fewer artificial lumens; dark rooms need more.
Controls how many fixtures the total lumen target is divided into.
LED is the most efficient modern choice; incandescent is the least efficient and mostly phased out.
Light output degrades with age and dirt. A factor of 0.80 is the standard planning assumption for homes.
Total lumens requiredComfortable general light
6,818lm

Total light output needed for adequate illumination at the IES-recommended level for this room.

Target illuminance150lux
Foot-candles equivalent13.9fc
Estimated wattage76W
Number of fixtures9
Room area20m2
Watts per m23.8W/m2
Downlight spacing guide1.3 to 2.0 m centre-to-centre
150 lux
Ambient<100General100-300Task300-600High-task600+
Lumens needed6,818
Total watts76
Fixtures9

You need 6,818 lm across 9 fixtures (76 W total).

  • A living typically targets 150 lux per IES guidelines; with your activity and daylight settings the effective target is 150 lux.
  • Your room needs about 6,818 lumens total - delivered by 9 fixtures drawing roughly 76 W of electricity.
  • At 3.8 W/m2 your lighting power density is well within the 10-15 W/m2 target for residential LED.

Next stepChoose a colour temperature (2700-3000 K for warm residential, 4000 K for kitchens and offices) and ensure your dimmer switch is LED-compatible.

 = Powered by OnlyCalculators