Total fitting lumens = target lux × area ÷ (utilisation factor × maintenance factor). This estimates average maintained illuminance for general lighting, without daylight.

Room targets are editable starting presets chosen for this tool, not certified minimums. Soft, balanced and bright select different targets within each preset. Dark finishes and taller rooms lower the automatic utilisation estimate.

The automatic factor is a deliberately simplified assumption, not manufacturer photometry: base 0.70 / 0.60 / 0.45 for light / mixed / dark finishes, divided by [1 + 0.15 × max(0, mounting height above the calculation surface − 2.5 m)], with a floor of 0.25. The displayed range varies this estimated factor by ±15% (bounded to 0.10–0.90); it is a sensitivity range, not a confidence interval. Enter a known factor to use a single calculated estimate.

Area-only input does not account for room shape. This tool does not calculate beam overlap, spacing, glare, uniformity or accent lighting. Narrow beams, indirect lighting and high ceilings need a project-specific layout using actual photometric files. Task areas may need separate lighting.

Method references: Eaton Lighting Design Guide · ERCO: maintenance factor.