Lighting
Illumination Uniformity Calculator
The purpose of Illumination Uniformity is to turn minimum illuminance and average illuminance into uniformity ratio. Keep the source condition with the saved result so later comparisons remain meaningful.
Enter values for Uniformity ratio
Use measurements from one operating condition.
From inputs to result
This page evaluates uniformity = minimum ÷ average × 100. The participating entries are Minimum illuminance and Average illuminance.
The defaults produce 66.67%. Replace them with measurements from one operating state.
Calculate uniformity ratio from minimum illuminance and average illuminance. When daylight factor affects the next decision, use Daylight Factor Calculator.
Measurements and entries
Keep lumens, candela, lux, and foot-candles on the correct geometric basis. A source note beside each entry makes the result reproducible.
A denominator entry cannot be zero. Confirm decimal placement whenever a source uses a different unit scale.
- Minimum illuminance
- Default example: 280 lx. Enter minimum illuminance in lx.
- Average illuminance
- Default example: 420 lx. Enter average illuminance in lx.
Checks that catch bad inputs
Values recorded at different operating points should not share one case.
Compare the magnitude with a quick independent estimate.
Assumptions and limitations
Use readings from a documented measurement grid.
Additional checks may be needed for driver efficiency, optical loss, surface reflectance, and beam-edge definition. Document which effects were checked elsewhere in the analysis.
Keep lumens, candela, lux, and foot-candles on the correct geometric basis.
Sensitivity check
Change Minimum illuminance from 280 lx to 336 lx as the sole changed variable. The two results are 66.67% to 80.00%.
The comparison demonstrates sensitivity, not a guaranteed field response.
Review the case step by step
Review minimum illuminance and the remaining entries as one case. If one value belongs to another temperature, load, or time period, separate the scenarios.
After calculating uniformity ratio, compare its magnitude with the fixture photometric file and the measured task plane. An independent order-of-magnitude check can reveal a misplaced decimal or unit prefix.
Document any effect handled outside this page, especially driver efficiency, optical loss, surface reflectance, and beam-edge definition. That note prevents a later reader from assuming the simple equation covered it.
Conditions that deserve another case
The calculator rejects values outside its stated field limits, but a numerically valid entry can still describe the wrong condition. Confirm minimum illuminance and average illuminance against the original source before saving the result.
Use an additional case for daylight variation, control behavior, depreciation, and spatial uniformity when that behavior is not negligible. Keep the baseline intact so the effect of each changed assumption remains visible.