Work out lighting level for task instantly with clear inputs, formula shown and shareable results.
The lumen method sizes lighting from the task requirement: total flux is required illuminance times area divided by the combined utilisation and maintenance factor. That factor, typically 0.4 to 0.6, accounts for light absorbed by surfaces, lost outside the working plane, and reduced by dirt and lamp ageing over the maintenance cycle.
Lumen method
Total lumens = required lux x area / (utilisation factor x maintenance factor)
Luminaire count
Count = ceil(total lumens / lumens per luminaire)
Preliminary estimate only. Lighting design must follow the applicable lighting standard for the task, including uniformity and glare limits.
Total lumens = required lux x area / (utilisation factor x maintenance factor). The lumen method sizes lighting from the task requirement: total flux is required illuminance times area divided by the combined utilisation and maintenance factor.
Lamps depreciate and fittings and surfaces collect dirt. Design standards specify maintained illuminance, the level at the end of the cleaning and replacement cycle, so the installation must start brighter.
This calculator takes 4 inputs: Required illuminance, Area to be lit, Luminous flux per luminaire, Utilisation and maintenance factor. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.