Calculating lighting is not hard if you start with the right question: not "how many lamps", but "how many lux does this room need". Lux (lx) is the amount of light per square metre, and different spaces have different targets under IES and local standards.
As a guide: a bedroom needs 100–150 lux, a living room 150–250, a kitchen work surface 300–500, an office 300–500, and production or precision work 500–750 and above. The first step is to decide what the room is used for.
The core formula is simple: total lumens = required lux × area (m²). For example, a 12 m² kitchen that needs 350 lux requires 12 × 350 = 4200 lumens. If one luminaire delivers 1400 lumens, you need about three.
For accuracy, add two corrections. A high ceiling (over 3 m) and dark walls absorb light, so add 10–20%. Luminaires also dim slightly over time, so a small margin is sensible.
So you do not have to do it all by hand, the site has a lighting calculator: enter the room size and its purpose and get the required lumens and the number of luminaires. If in doubt, our specialists will help you pick the right model from the Electrica Group catalogue.
