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Lighting Level For Task Calculator

Work out lighting level for task instantly with clear inputs, formula shown and shareable results.

About Lighting Level For Task Calculator

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.

Formulas

Lumen method

Total lumens = required lux x area / (utilisation factor x maintenance factor)

Luminaire count

Count = ceil(total lumens / lumens per luminaire)

Worked example

With the default values below, Lighting Level For Task Calculator returns Luminaires required of 14. Change any input above and every figure here is recalculated in your browser.

Inputs used

Required illuminanceone of Rough work or circulation — 200 lux, General office and assembly — 500 lux, Detailed inspection work — 1000 lux
General office and assembly — 500 lux
Area to be litminimum 0.1 m²
40 m²
Luminous flux per luminaireminimum 1 lm
3,000 lm
Utilisation and maintenance factoraccepts 0.1–1
0.5

Results

Luminaires required
14
Total luminous flux required
40,000 lm
Illuminance achieved
525.0 lux
Estimated load at 100 lm/W
420.0 W

Step by step

  1. 1Values used
  2. 2Lumen method
  3. 3Luminaire count
  4. 4Luminaires required= 14
  5. 5Total luminous flux required= 40,000 lm
  6. 6Illuminance achieved= 525.0 lux
  7. 7Estimated load at 100 lm/W= 420.0 W

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 1 decimal place, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Preliminary estimate only. Lighting design must follow the applicable lighting standard for the task, including uniformity and glare limits.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Preliminary estimate only. Lighting design must follow the applicable lighting standard for the task, including uniformity and glare limits.

Frequently Asked Questions

How is the Lighting Level For Task figure worked out?

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.

Why is the maintained level lower than the initial level?

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.

What values do I need to enter?

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.

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