Daylighting Factor Calculator

Calculate the Average Daylight Factor for a room based on window area, glass transmittance, room geometry, and surface reflectance.

Room Width (ft)

Room Depth (ft)

Ceiling Height (ft)

Net Glazing Area (sq ft)

Glass Transmittance (0-1)

Avg Surface Reflectance (0-1)

Sky Angle Factor (0-1)

Tab to move between fields

Daylight Factor (%)

1.06

Window-to-Floor Ratio (%)10%

Estimated Daylight Autonomy (%)21%

Daylight Uniformity (%)81%

Lighting Savings (kWh/yr)106

Total Surface Area (sq ft)1,230

RatingMarginal — supplemental lighting recommended

How to Use This Calculator

Enter Room Width and Depth in feet and the Ceiling Height in feet.
Enter Net Glazing Area in sq ft (total glass area excluding frames).
Enter Glass Transmittance (visible light transmittance from the window spec) and Average Surface Reflectance.
Enter Sky Angle Factor reflecting how much of the sky dome the window sees (0.5 unobstructed).
Review Daylight Factor percentage, Daylight Autonomy, and Lighting Savings in kWh/year.

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