Lighting Calculator
Estimate required lumens, fixture quantity, average spacing, installed wattage and annual electricity cost for a rectangular room.
Default project preview
6 fixtures
Design lumens
16,071
Average spacing guide
7.1 ft
Installed load
168 W
Annual electricity
367.9 kWh
Calculator
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Enter the project details and calculate a rounded material estimate.
Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
Raw lumens = room area × target light level. Design lumens divide raw lumens by utilization and maintained-light factors. Fixtures = round up (design lumens ÷ fixture lumens).
FAQ
Lighting Calculator questions
What is a foot-candle?+
One foot-candle is one lumen per square foot. One lux is one lumen per square metre.
Why are utilization and light-loss factors used?+
Not all fixture lumens reach the work plane, and output declines with dirt, ageing and operating conditions.
Does equal spacing guarantee uniform light?+
No. Fixture beam shape, mounting height and room surfaces determine uniformity.