Use this calculator to estimate how many recessed lights you need for any room, based on room size, ceiling height, and the type of lighting you want.
How the Calculation Works
The number of fixtures is calculated using the standard lighting design formula:
Number of Fixtures = (Room Area × Required Foot-Candles) ÷ (Lumens per Fixture × 0.6)
The 0.6 factor is the coefficient of utilization — a standard estimate accounting for light lost to walls, ceiling, and furnishings in a typical room.
Foot-Candle Reference by Room Type
Different spaces require different light levels, measured in foot-candles (fc). General living areas typically need 10–20 fc, kitchens and bathrooms 35–70 fc, and task-heavy areas like offices up to 50 fc.
Fixture Spacing Guidelines
For even light distribution, space fixtures a distance equal to half your ceiling height from the walls, and equal to your ceiling height between fixtures. In a 9-foot ceiling room, that means fixtures sit about 4.5 feet from walls and 9 feet apart from each other.
Choosing the Right Fixture Size
A 6-inch recessed fixture is the most common choice for residential spaces. Use 4-inch fixtures for accent or task lighting, and larger 8-inch fixtures for high-ceiling commercial or warehouse settings.
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