Emergency Lighting Illumination Calculator
Estimate direct horizontal illuminance at one point from a supplied fixture candela value and mounting geometry.
Enter photometric value and geometry
Use a photometric value in the direction from fixture to the evaluation point.
Estimated horizontal illuminance
About this calculator
Estimate direct horizontal illuminance at a single point on a horizontal plane from one fixture’s candela in the direction of that point. Enter fixture mounting height and horizontal offset.
Obtain photometric candela values from the fixture data for the applicable emergency operating mode.
Method and assumptions
Distance = √(mounting height² + horizontal offset²). Horizontal illuminance in foot-candles = candela × cosine of the incidence angle ÷ distance², with distance in feet.
This direct-light point model ignores fixture distribution interpolation and environmental effects. It is not a complete lighting layout or code determination.
FAQs
Which candela value should I enter?
Use a photometric candela value in the direction from the fixture toward the evaluation point, taken from the exact fixture photometric data.
Does this calculate egress-path coverage?
No. This estimates one point from one direct-light source. Full layout analysis requires photometric distribution and geometry for all fixtures, plus the applicable design criteria.
Sources
Use the fixture manufacturer’s emergency-mode photometric data and the applicable project design criteria.