Room Lighting Calculator

Multiply the floor area in square feet by the target foot-candles. A 12 by 10 foot room is 120 square feet, and at 30 foot-candles it needs 3,600 lumens.

A foot-candle is one lumen falling on one square foot of surface. It measures how brightly a surface is lit, which is why it works as the target level you dial in for a task.

As a rough guide, living rooms sit around 10 to 20, kitchens and bathrooms around 30 to 40, and detailed work areas like a workshop or study 50 or more. Pick the higher end for older eyes or precise tasks.

Check the lumen rating on the package rather than the watts. A 60 watt incandescent puts out roughly 800 lumens, and an equivalent LED lists the same 800 while drawing far fewer watts.

Partial bulbs do not exist, so the count is rounded up to guarantee the room reaches at least the target. The one exception is an even split, like 3,200 lumens with 800-lumen bulbs, which stays at exactly 4 rather than jumping to 5.

Yes. Leave the Lumens/bulb field blank and the tool still shows the floor area and total lumens needed, with the Bulbs needed card prompting you to add a bulb output when you want it.

No. This is a straightforward area times foot-candles estimate, so a very tall ceiling, dark walls, or heavy shades will call for more light than the baseline suggests. Treat the result as a starting point.

Break an L-shaped or irregular room into rectangles, size each one, and add the lumen totals. You can also enter an average length and width, though splitting the space is more accurate.

Yes. The calculation runs entirely in your browser with nothing uploaded, so the room measurements you enter stay on your device.