Lux is lumens spread over an area, so total light equals lux times area in square meters. Enter your target level and the area below to size the lumens needed on the surface.
How to convert lux to lumens
Multiply the target lux by the area in square meters. If the area is in square feet, convert it first (1 square foot is 0.092903 square meters). The result is the light that must reach the surface, so choose fixtures rated above it to cover optical and mounting losses.
Lumens for a target level (per area)
| Area | At 300 lux | At 500 lux |
|---|---|---|
| 10 sq m | 3,000 lm | 5,000 lm |
| 20 sq m | 6,000 lm | 10,000 lm |
| 50 sq m | 15,000 lm | 25,000 lm |
Frequently asked questions
How do I convert lux to lumens?
Multiply lux by the lit area in square meters. 500 lux over 10 square meters is 5,000 lumens delivered.
What is the difference between lux and lumens?
Lumens measure total light emitted; lux measures how concentrated it is on a surface (lumens per square meter). The same lumens give more lux on a smaller area.
How many lumens to light a room?
Pick a target lux, then multiply by floor area in square meters. A 20 sq m office at 400 lux needs about 8,000 lumens delivered, before margin.
Does this account for beam angle and distance?
No. It uses lumens = lux x area. For a spotlight, compute the illuminated area from beam angle and distance first, then use this tool.
Is delivered lumens the same as fixture lumens?
No. A fixture must emit more than the delivered figure to cover optical, mounting, and room losses, so choose fixtures rated above it.
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