Lux Illumination Calculator

Illuminance in lux: lumens per square metre

Illuminance is the luminous flux that actually reaches a surface: lux = lumens / m². Take a 9 W LED bulb putting out about 800 lm; spread that evenly across an 8 m² room and the floor sees roughly 100 lux. In Brazil the NBR ISO 8995-1 sets minimums by task: 100 lux for hallways and storage, 150–300 lux for living rooms, 300–500 lux for kitchens, 500 lux for office desks, and 1.000+ lux for surgical fields and fine inspection. Watch out for indirect light, dirty fixtures and high ceilings, since each one cuts into the lux you actually get.

Applications

Lighting design for homes and commercial projects, NR-17 visual ergonomics checks on offices and workstations, industrial production lines, photography studios, retail visual merchandising — the calculation feeds all of them.

FAQ

What's the difference between lumens and lux? Lumens count the total light a source emits. Lux tells you how much of that light lands on a surface, which depends on the distance and the area it's covering.

Does the formula account for walls and reflections? No. The basic average is a theoretical figure. On a real project you'd bring in a utilisation factor and a maintenance factor to account for absorption and aging.

How many LED bulbs do I need for an office? Target 500 lux at the desk. In a 12 m² room that works out to around 6.000 lumens total, so roughly 7 bulbs at 800 lm each.