Lighting calculator

Enter the floor area of the room, the illuminance you want and the luminous flux of the lamp, and we show how many lamps it takes.

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How does the lighting calculator work?

The required luminous flux comes from the product of the illuminance and the floor area, corrected with two factors:

• Φ = E · A / (UF · MF): E is the target illuminance (lux), A the floor area (m²), UF the utilisation factor and MF the maintenance factor.
• The number of light sources is Φ divided by the luminous flux of one source, rounded up; the illuminance achieved is calculated back from the whole number of lamps.

If you also enter the power of one light source, the calculator shows the total power and the power per square metre.

What to watch for

You enter the target illuminance yourself, the calculator does not suggest a value: take the value that suits the use of the room from the design requirements or agree it with the client. The utilisation factor (0.5 by default) depends on the size of the room, the colour of the walls and the ceiling, and the luminaire; the maintenance factor (0.8 by default) estimates the loss of luminous flux due to ageing and dirt. Both can be changed.

Limits of the calculation

The calculator works with a simple average illuminance: it does not take into account the placement of the lamps, the light distribution, glare or colour rendering. The result is for guidance only; the final lighting design must be prepared by the designer.

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