How this calculator works
Lighting guidelines are given in foot-candles, which is just lumens per square foot. Living rooms and bedrooms need about 10 to 20, kitchens and work areas 30 to 50, and bathrooms with grooming mirrors somewhat more. Multiply by the room area to get the total lumens. Then divide by the lumens each bulb gives off.
Worked example: a 12 × 12 ft living room (144 ft²) at 15 lumens per ft² needs 2,160 lumens, or three 800-lumen bulbs (a 60-watt-equivalent LED each). With LEDs at 90 lumens per watt, that is 24 watts.
Tips before you buy
- Layer the light: ambient (ceiling), task (under-cabinet, desk lamps) and accent. Total lumens are only a starting point.
- Pick the colour temperature to suit the room: 2700 K (warm) for living rooms and bedrooms, 3000 to 4000 K for kitchens and bathrooms, and 5000 K for workshops.
- Dimmers let you set the level for the time of day. Make sure the bulbs and dimmer are compatible.
- LEDs use about one sixth of the electricity of incandescent bulbs for the same brightness, and last much longer.
Tools & materials for this project
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Frequently asked questions
How many lumens do I need for a room?
Multiply the area by the lumens per square foot for the room: about 10 to 20 for living rooms and bedrooms, 30 to 40 for kitchens, and 40 or more for bathrooms, offices and workshops.
How many lumens is a 60 watt bulb?
About 800 lumens. A 40 W equivalent is about 450, a 75 W is about 1,100 and a 100 W is about 1,600.
How many lumens do I need for a kitchen?
About 30 to 40 lumens per square foot, so a 12 × 12 ft kitchen needs 4,300 to 5,800 lumens in total, including task lighting over counters.
Related calculators & guides
Estimates only. Results assume standard materials and simple shapes. Supplier products vary, and the final call on quantity, structure and safety is yours. Check your local code and your supplier's guidance before ordering.