Room Lighting Calculator
Work out the light a room needs. Enter the room size and a target level in foot-candles to get total lumens, then add a bulb output to see how many bulbs.
How to size room lighting
- Enter the room length and width in feet.
- Choose a target light level in foot-candles for how the room is used.
- Read the total lumens the room needs.
- Enter the lumens per bulb to see how many bulbs to fit.
Examples
12 by 10 ft room at 30 foot-candles
120 sq ft, 30 foot-candles, 800 lumen bulbs
3,600 lumens needed, about 5 bulbs
Frequently asked questions
How many lumens does a room need?
Multiply the floor area in square feet by the target foot-candles. A 120 square foot room at 30 foot-candles needs 3,600 lumens.
What is a foot-candle?
A foot-candle is one lumen falling on one square foot. It measures how bright a surface is lit, so it sets the target light level.
What foot-candle level should I use?
Living rooms use about 10 to 20, kitchens and bathrooms about 30 to 40, and detailed work areas 50 or more.
How do I find a bulb's lumens?
Look on the package for the lumen rating. A 60 watt incandescent is about 800 lumens, and LEDs list the same figure.
Why round the bulb count up?
Partial bulbs do not exist, so the count rounds up to make sure the room reaches at least the target light level.
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