1 lumen equals 1 lux when the luminous flux is spread evenly over 1 square meter. So, 1 lumen per square meter results in 1 lux.
The conversion from lumen to lux depends on the area the light is illuminating. Lux measures illuminance, which means how much luminous flux (in lumens) hits a surface area, measured in square meters. Thus, 1 lumen uniformly distributed over 1 square meter produces 1 lux.
Conversion Tool
Result in lux:
Conversion Formula
The formula to convert lumen to lux is:
lux = lumen ÷ area (in square meters)
This works because lux measures illuminance, which is the amount of light hitting a certain surface area, while lumen measures total light output. When you divide the total luminous flux (lumens) by the illuminated area, you get how intense the light is on that surface (lux).
Example:
- You have 1 lumen of luminous flux.
- The light spreads over 1 square meter.
- lux = 1 lumen ÷ 1 m² = 1 lux.
Conversion Example
- Convert 50 lumens over 2 square meters:
- Divide 50 lumens by 2 m².
- 50 ÷ 2 = 25 lux.
- So, 50 lumens spread on 2 m² equals 25 lux.
- Convert 100 lumens over 5 square meters:
- 100 ÷ 5 = 20 lux.
- Meaning, the illuminance is 20 lux on that surface.
- Convert 10 lumens over 0.5 square meters:
- 10 ÷ 0.5 = 20 lux.
- The smaller the area, the higher the lux for same lumens.
- Convert 0.5 lumens over 1.5 square meters:
- 0.5 ÷ 1.5 ≈ 0.3333 lux.
- Lower light output or larger area lowers lux value.
- Convert 200 lumens over 10 square meters:
- 200 ÷ 10 = 20 lux.
- Shows how distribution area influences lux.
Conversion Chart
| Lumen | Lux (assuming 1 m²) |
|---|---|
| -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 |
Reading the chart, you can directly see that the lux value equals the lumen value assuming the light spreads over an area of 1 square meter. Negative values may be theoretical or used in calculations but represent no physical luminous flux in practical sense.
Related Conversion Questions
- How many lux are in 1 lumen when the light covers 1 square meter?
- Can 1 lumen produce 1 lux on any surface size?
- What area must 1 lumen illuminate to create 5 lux?
- Why does lux value change if I keep lumens constant at 1?
- Is 1 lumen always equal to 1 lux?
- How to calculate lux from 1 lumen if area is unknown?
- What factors affect converting 1 lumen to lux in real life?
Conversion Definitions
Lumen: The lumen is a unit measuring the total quantity of visible light emitted by a source per second. It quantifies luminous flux, describing how bright a lamp or light source appears regardless of direction. The higher the lumen, the brighter the light.
Lux: Lux measures illuminance, which is the amount of luminous flux falling on a surface per unit area. One lux equals one lumen per square meter. It reflects how much light is actually reaching a surface, useful in assessing lighting conditions in rooms or outdoors.
Conversion FAQs
Can you convert lumens to lux without knowing the area?
No, because lux depends on how the light spreads over an area. Lumens measure total output, but lux measures intensity per square meter. Without area, you can’t determine lux from lumens alone.
Why can lux be higher than lumens in some cases?
Lux can appear higher if the same lumens are focused onto a smaller area, increasing illuminance. However, lux itself is not greater than lumens; it’s just a different measurement relative to area.
Are negative lumens or lux physically possible?
Negative values in lumens or lux are not physically meaningful. They may appear in calculations or data processing as errors or placeholders but don’t represent real light quantities.
What happens to lux when the illuminated area increases but lumens stay the same?
Lux decreases because the same amount of light spreads over a larger area, reducing the light intensity per square meter.
Is the conversion formula the same for all light sources?
The formula lux = lumens ÷ area applies universally, but real-world factors like reflection, absorption, and beam angle affect actual illuminance.