What is lux? How many lux you need per room

Lux (lx) is the unit of illuminance: the amount of light falling on a surface. One lux is one lumen per square metre. Whereas lumens tell you how much light a lamp emits, lux tells you how much light actually reaches, for example, a desk, workbench or floor.

Office with desks and bright ceiling lighting — For office work, 500 lux on the desk is the guide value.

The difference between lumens and lux

A 4,000-lumen lamp gives a lot of lux up close, but much less at a greater distance or spread over a large area. The lux at a given spot therefore depends on the light output, the distance, the beam angle and the reflection from walls and ceiling.

How many lux do you need?

The European standard EN 12464-1 gives guide values for indoor workplaces. Some examples:

Room or task	Guide value
Corridors and circulation areas	approx. 100 lux
Warehouse and storage	approx. 100 to 200 lux
Canteen, toilet, changing room	approx. 200 lux
Office work, reading, writing	500 lux
Fine work, technical drawing	750 lux or more

At home there are no fixed requirements. As a guide: a living room generally needs approx. 100 to 200 lux, a kitchen worktop or desk 300 to 500 lux.

How do you measure lux?

You measure lux with a lux meter or, as a rough guide, with a smartphone app. Measure at working height, for example on the desk, at several points in the room.

More lux with fewer lamps

With efficient luminaires you achieve the desired light level with less power. In high halls, LED high bay luminaires provide enough lux on the floor; in offices, LED panels do the job.