Lighting Layout Calculator
Determine the number of light fixtures needed for a room using the lumen method and desired foot-candle level.
Fixtures Needed
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Fixtures Needed vs Room Length
Formule
## Lumen Method for Lighting Design **N = (Area x FC) / (Lumens per Fixture x CU x MF)** Where FC is the target foot-candle level, CU is the coefficient of utilization (depends on room shape and reflectance), and MF is the maintenance factor (accounts for dirt and lamp aging).
Exemple Résolu
20x15 ft office at 50 fc using 3,200-lumen fixtures, CU=0.6, MF=0.8.
- 01Area = 20 x 15 = 300 sq ft
- 02Lumens needed = 300 x 50 = 15,000 lm
- 03Effective per fixture = 3200 x 0.6 x 0.8 = 1,536 lm
- 04Fixtures = 15,000 / 1,536 = 9.77, round up to 10
Questions Fréquentes
What foot-candle level do I need?
General office: 30-50 fc. Retail: 50-75 fc. Warehouse: 10-30 fc. Kitchen: 50-75 fc. These values come from the Illuminating Engineering Society (IES) recommendations.
What is the coefficient of utilization?
CU represents how effectively light reaches the work surface. It depends on fixture type, room dimensions, and surface reflectances. Typical values range from 0.4 to 0.8.
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