Lux Level Calculator
Enter the output and count of your fittings, room area, and planning factors to estimate average lux at the working plane.
Average illuminance: lx
Formula: E = lumens × fittings × UF × MF ÷ area
Planning estimate; does not model placement, glare, or local variation.
A QUICK WALKTHROUGH
How to use this tool
- Enter lumens per fitting, the number of fittings, and the room area in square metres.
- Enter utilisation and maintenance factors as decimals between 0 and 1.
- Calculate average illuminance using E = lumens × fittings × UF × MF ÷ area.
The lumen method
This calculator estimates average illuminance across a working plane. Utilisation factor represents the share of fitting output reaching that plane; maintenance factor accounts for expected depreciation and dirt.
Planning estimate
Use fitting or luminaire lumens where available. The result does not model fitting placement, glare, room reflectance, beam shape, or local dark and bright areas.
Factors are assumptions
UF and MF are decimal factors from 0 to 1. A value of 0.5 means half of the installed lumens is retained for the calculation; choose values from appropriate design data when available.
GOOD TO KNOW
Common questions
What is a utilisation factor?
It is the fraction of a fitting’s output expected to reach the working plane after room and fitting effects.
What is a maintenance factor?
It allows for light loss over the maintenance period from lumen depreciation and dirt.
Is this a lighting design?
No. It is an average planning estimate and does not replace a proper photometric design or on-site measurement.