Indoor Lighting Calculator
Estimate the number of LED fixtures required to reach your target Foot-candles.
Room Dimensions
Lighting Requirements
Required Fixtures
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The Zonal Cavity Method (Lumen Method)
In the United States, lighting designers use Foot-candles (fc) to measure illuminance (light hitting a surface). To find out how many fixtures are needed to light a room evenly, the industry uses the Lumen Method.
Total Lumens Required:
$$ \Phi = \frac{\text{Area } (ft^2) \times \text{Foot-candles}}{CU \times LLF} $$
Where:
- Area = Length x Width of the room in Square Feet.
- CU (Coefficient of Utilization) = The percentage of light that actually reaches the work plane, depending on wall reflectance.
- LLF (Light Loss Factor) = Depreciation of light due to dirt and LED aging.
Note: This calculator uses a combined Factor (CU x LLF) to provide a fast and reliable estimate for contractors.