How this calculator works
Different rooms need different light levels, measured in foot-candles (lumens per square foot). A kitchen or bathroom needs brighter task lighting than a bedroom or living room. This calculator multiplies your room’s area by a typical recommended foot-candle level for the room type you choose, then divides by your bulb’s lumen output to estimate how many bulbs you need.
The formula
Total lumens needed = Room area (sq ft) × Recommended foot-candles for that room type. Bulbs needed = Total lumens needed ÷ Lumens per bulb, rounded up.
These foot-candle levels are general interior-lighting guidelines. Actual needs vary with ceiling height, wall and furniture color, natural light, and personal preference, and layered lighting (ambient, task, and accent) often works better than one single light source.