Lighting Design Calculator
Estimate how many light fittings you’ll need
Enter your room size, brightness level and fixture details. The calculator will estimate how many fittings you need and what the energy use might look like.
1. Lighting target
Pick a space type – it fills in a typical brightness level automatically.
How bright you want the space to be. Offices ~500 lux, corridors ~200 lux.
Allows for light loss over time. Leave at 0.8 if unsure.
2. Room size
Room length in metres.
Room width in metres.
Floor to ceiling height.
If lights hang below the ceiling (e.g. suspended).
Usually the height of desks or benches.
Spacing ratio. 1.2 suits most rooms – higher = fewer fittings.
3. Surface reflectances
Light colours reflect more – typical ceiling 70%.
Average wall reflectance.
Floors are usually darker, around 20%.
4. Luminaire info
How much light one fitting produces (check datasheet).
Electrical power draw per fitting.
UF describes how efficiently light reaches the working plane. Leave unchecked for auto mode.
5. Energy settings
Roughly 8 h/day × 5 days/week ≈ 2000–3000 h/year.
For annual energy cost – UK average around 20 p/kWh.
Results summary
See how many fittings you’ll need, expected brightness, and estimated energy use.
Area (m²)
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Luminaires needed
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Rows × per row
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Installed power (kW)
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Predicted illuminance (lux)
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Energy use (kWh / year)
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Tip: This gives a quick visual estimate — for detailed designs or compliance checks, use full photometric software.
