Daylight Factor Calculator

How Daylight Factor works

For Daylight Factor, use DF = indoor ÷ outdoor × 100. Daylight Factor uses Indoor illuminance, Outdoor illuminance to report Daylight factor.

With the loaded values, daylight factor evaluates to 2.50%. Test indoor illuminance separately and preserve the baseline daylight factor.

Inputs for Daylight Factor

Indoor illuminance and Outdoor illuminance belong to Daylight Factor. Keep source units with indoor illuminance.

The Daylight Factor defaults demonstrate arithmetic only. Replace indoor illuminance with case-specific data.

Indoor illuminance

Example entry: 300 lx.

Outdoor illuminance

Example entry: 12000 lx.

Reading the Daylight Factor result

This output represents Daylight Factor.

Before selecting equipment for Daylight Factor, compare daylight factor with available ratings and operating limits.

Measurement and units

Photometric results depend on fixture distribution, reflectance, mounting, maintenance, and the measured task plane. Check prefixes on indoor illuminance. Continue to LED Driver Current Calculator for driver output power.

Keep the indoor illuminance unit and measurement point consistent across Daylight Factor cases.

Limits of this calculation

Both readings should be simultaneous under comparable sky conditions.

Only the listed Daylight Factor inputs contribute to daylight factor. Unentered effects remain outside Daylight Factor. Use Light Fixture Spacing Calculator.

A useful Daylight Factor comparison

Record daylight factor before testing a different indoor illuminance value.

Document the alternate indoor illuminance source.

Questions about Daylight Factor