Room Lighting Calculator
Calculate the total lumens needed and the recommended number of light fixtures for a room based on its size and desired brightness.
ft
ft
foot-candles
Check the bulb or fixture packaging for its lumen output
Results
Recommended Fixtures
3
Room Area
120 sq ft
Total Lumens Needed
1,800 lm
How the Room Lighting Calculator Works
Enter your room's length and width, and choose a room type preset (or a custom foot-candle level) for how brightly lit the space should be. One foot-candle equals one lumen per square foot, so multiplying the room's area by the desired foot-candle level gives the total lumens needed. Divide that by the lumen output of the fixtures or bulbs you plan to use to get a recommended fixture count.
Example
A 12 ft × 10 ft living room (120 sq ft) lit to a typical 15 foot-candle level needs 120 × 15 = 1,800 lumens total. With fixtures rated at 800 lumens each, that's 1,800 ÷ 800 = 2.25, rounded up to 3 fixtures.
Common Use Cases
- Planning how many ceiling fixtures or lamps a room needs during a renovation.
- Choosing the right bulb wattage/lumen output for a new light fixture.
- Comparing lighting needs between differently-sized rooms.
- Checking whether an existing lighting setup meets a recommended brightness level.
FAQs
What foot-candle level should I use?
It depends on the room's purpose — relaxing spaces like living rooms and bedrooms typically use 10-20 foot-candles, task-heavy spaces like kitchens and bathrooms use 30-40, and focused work areas like home offices often use 50 or more. The room type presets above set a reasonable starting point, which you can always adjust.
Should I count lumens or watts when shopping for bulbs?
Lumens measure actual brightness output, while watts measure energy consumption — modern LED bulbs produce far more lumens per watt than older incandescent bulbs. Always check the lumens figure on the packaging rather than assuming a wattage equivalent.
Does this account for natural light or room color?
No — this gives a baseline lumen target based on room size and desired brightness alone. Rooms with significant natural daylight or light-colored walls and ceilings that reflect more light may need slightly less artificial lighting than the calculated figure suggests.