Lighting Illuminance Uniformity Ratio
Avg/min, max/min, and U0 = min/avg from a grid of illuminance readings, against a target ratio.
Example
You enter
- Illuminance readings (fc or lux, comma or space separated) 50, 45, 60, 55, 40
- Target max/min (optional, e.g. 3) 3
You get
- Avg min 1.25
- Max min 1.5
- Overall uniformity U0 (min/avg) 0.8
No published worked example is on file for this calculation. It is checked against a hand-worked derivation of its method and an independent reference test.
Details, formula, and sources
ScopeReadings 50/45/60/55/40 fc -> 1.25 avg/min, 1.50 max/min; a patchy 70/20/65/25/30 fails a 3:1 target the average hides. The IES RP for the space governs.
Formula or tableavg/min, max/min, U0 = min/avg over a grid of readings; pass if avg/min <= target and max/min <= target.
Source and editionThe IES illuminance uniformity ratios (avg/min, max/min, U0), by name.
Free accessThe uniformity ratios and target values are published in the IES recommended practices for each space type. The IES RP governs the target.
What governsEstimate. AHJ and licensed professional govern.
API field namesreadings, target_maxmin, avg_min, max_min, U0
- Ratios avg/min, max/min, U0 = min/avg over the reading gridIES recommended practice
- Targets ~3:1 max/min for offices; tighter for task areasIES RP
- Equal-weight grid treats readings as an equal-weight grid; grid spacing/meter not verifiedscope of this tile