1 lumen equals 1 lux when the light is evenly distributed over an area of 1 square meter.
Lux measures illuminance, which is how much light hits a surface, while lumen measures total light output. So, 1 lumen spread over 1 square meter results in 1 lux. If the same lumen output is spread over larger area, lux decreases, and vice versa.
Conversion Tool
Result in lux:
Conversion Formula
The formula for converting lumens to lux depends on the area illuminated. Lux is lumens divided by the area in square meters.
Lux = Lumens / Area (in m²)
This formula works because lumen quantifies total luminous flux emitted, while lux measures how that flux spreads over a surface. When 1 lumen light covers 1 square meter, the illuminance is 1 lux.
Example:
If you have 50 lumens spread over 5 square meters, then lux = 50 ÷ 5 = 10 lux.
Conversion Example
- Example 1: 10 lumens over 2 m²
- Take 10 lumens
- Divide by 2 m²
- 10 ÷ 2 = 5 lux
- The illuminance is 5 lux
- Example 2: 100 lumens over 4 m²
- Start with 100 lumens
- Divide by 4
- 100 ÷ 4 = 25 lux
- Area receives 25 lux of light
- Example 3: 500 lumens over 10 m²
- 500 lumens total
- Divided by 10 square meters
- 500 ÷ 10 = 50 lux
- Illuminance is 50 lux
- Example 4: 75 lumens over 3 m²
- 75 lumens
- Divide by 3 m²
- 75 ÷ 3 = 25 lux
- Surface lit at 25 lux
Conversion Chart
| Lumens | Lux (assuming 1 m² area) |
|---|---|
| -24.0 | -24.0 |
| -20.0 | -20.0 |
| -15.0 | -15.0 |
| -10.0 | -10.0 |
| -5.0 | -5.0 |
| 0.0 | 0.0 |
| 1.0 | 1.0 |
| 5.0 | 5.0 |
| 10.0 | 10.0 |
| 15.0 | 15.0 |
| 20.0 | 20.0 |
| 26.0 | 26.0 |
This chart shows lumens values and their equivalent lux, assuming the light spreads over 1 square meter. To use it for different areas, divide the lumens value by your surface area in square meters to get lux.
Related Conversion Questions
- How many lux does 1 lumen produce on a 1 square meter surface?
- What is the lux value if 1 lumen spreads over 2 square meters?
- Can 1 lumen equal 1 lux always, or does area affect it?
- If I have 1 lumen, how do I find the lux on 0.5 m²?
- Is 1 lumen the same as 1 lux in a lighting measurement?
- How to convert 1 lumen to lux when area is unknown?
- What unit should be used to measure brightness: lumen or lux for 1 unit?
Conversion Definitions
Lumen: Lumen measures the total amount of visible light emitted by a source in all directions. It quantifies luminous flux, showing how bright a bulb or light source appears, regardless of the direction the light travels.
Lux: Lux measures illuminance or how much luminous flux falls on a surface per unit area, equal to one lumen per square meter. It tells how bright a surface will be when lit by a certain amount of lumens.
Conversion FAQs
Why does the area affect the conversion between lumens and lux?
Because lumens measure total light output, and lux measures light intensity per area, changing the surface area changes how concentrated the light is. The same lumen spread over a bigger area means lower lux, since light is less concentrated.
Can I convert lumens to lux without knowing the area?
No, lux depends on area size. Without surface area, you can’t accurately calculate lux from lumens. You need the illuminated surface in square meters to find lux.
Is 1 lumen always equal to 1 lux?
Only if the 1 lumen is uniformly spread over exactly 1 square meter. If the area is different, the lux changes proportionally. So the equality applies only under those conditions.
Why are some lux values negative in the chart?
Negative lumens and lux have no physical meaning, but are included in the chart for completeness or hypothetical calculations. Normally, lumens and lux are zero or positive.
How to measure lux in a room using lumens?
Measure total lumens from all light sources, then divide by the room’s surface area in square meters. This gives an estimation of the average lux illuminating the room.