Lighting Calculator: Lumens Needed Per Room

How to calculate lighting for a room

1. 1

   Measure the room

   Measure the room’s length and width in feet to get its floor area.

2. 2

   Select the room type

   Choose the room’s primary use — kitchens and bathrooms need strong task lighting, home offices need focused working light, and living rooms and bedrooms need softer ambient levels.

3. 3

   Enter your bulb brightness

   Enter the lumen output of the bulbs or fixtures you plan to use; it is printed on every bulb package (an 800-lumen bulb is the classic 60-watt equivalent).

4. 4

   Distribute the fixtures

   The calculator gives total lumens and the number of bulbs needed. Spread them across at least two layers — ambient ceiling light plus lamps or task lights — rather than one bright central fixture.

The math behind this calculator

Lighting professionals size rooms in foot-candles (one lumen per square foot). This calculator multiplies your floor area by the recommended foot-candle level for the room type: about 70 for kitchens and bathrooms where task lighting matters, 50 for home offices, and 15–20 for living rooms, bedrooms, and dining rooms where atmosphere leads. Prefer your own numbers? Pick the custom target option and set any foot-candle level, and enter the exact lumen output of your bulbs.

Total lumens ÷ your bulb’s lumen output, rounded up, gives the bulb count. Two practical adjustments: dark walls and floors absorb light, so add roughly 10–20% for moody color schemes; and dimmers effectively let one room serve multiple light levels, so when in doubt, install the higher count on a dimmer.

Frequently asked questions