Lighting a 20 × 20 ft basement
Total light needed
12,000lumens
400 ft² × 30 foot-candles
| Room area | 400ft² |
|---|---|
| Target light levelIES guidance for a basement | 30foot-candles |
| Total lumens | 12,000lm |
| Colour temperatureraise it if the ceiling is low and dark | 4000K |
| Bulbs (800 lm each) | 15bulbs |
| Recessed cans (4 ft spacing)480 lm each | 25fixtures |
- Room
- basement
- Width
- 20 ft
- Length
- 20 ft
Where 12,000 lumens comes from
Lighting is specified in foot-candles — lumens landing on each square foot of the surface you care about. A basement is worked to 30 foot-candles. Across 400 ft² that is 12,000 lumens in total.
Split it up
One fixture putting out 12,000 lumens and 25 fixtures adding up to the same number light a room very differently. A single source throws hard shadows and glare; several spread the light and make the room feel larger. Aim for layers — ambient, task, and something low for the evening.
Colour temperature
4000K suits this room. Warmer light reads as relaxed and is what you want where people wind down; cooler light keeps edges and colours crisp, which matters where there is work to do.
Notes
- Foot-candles are lumens per square foot at the work surface. Ceilings above 9 ft, dark walls or dark flooring all eat light — add roughly 10% per extra foot of ceiling height.
- Spread the total across several fixtures rather than one bright source. One 12,000 lm fixture and 25 smaller ones add up the same but look completely different.