Use an editable target lux, utilisation and light-loss factors to estimate lumens, whole fixtures, existing-light shortfall and a simple layout to verify on site.
How many fixture lumens are required for this planning target, and how far is the existing setup from it?
Lux is illuminance on a surface; lumens are source output and watts are power. The simplified lumen method makes utilisation and light loss explicit, but the final installation still needs product photometry and an on-site lux check.
Method
Required lumens = target lux × area ÷ (utilisation factor × light-loss factor). Whole fixtures round up by exact label lumens; existing delivered lux uses the same declared assumptions.
Important limitation
The tool does not perform IES point-by-point modelling, glare or emergency-lighting compliance. Preset/default values are editable planning assumptions, never legal or professional targets.
How to use the result safely
Treat the result as a transparent planning ledger. Stop before purchase or installation when an exact specification, rate, structure or measured condition is unknown.
