1 lumen equals 1 lux when the light is evenly distributed over an area of 1 square meter.
Lumen measures the total amount of visible light emitted by a source, while lux quantifies the intensity of that light on a surface area. So, if 1 lumen falls on 1 square meter, the illuminance is 1 lux.
Conversion Tool
Result in lux:
Conversion Formula
The formula to convert lumen to lux depends on the surface area over which the light spreads. Lux is defined as lumens divided by the area in square meters.
Mathematically, lux = lumens / area (m²).
This works because lumen is the total light output, while lux measures how concentrated that light is per unit area. Without knowing the area, converting lumen directly to lux can’t be done precisely.
For example, if 1 lumen shines uniformly on 1 m²:
- lux = 1 lumen / 1 m² = 1 lux
If the same 1 lumen spreads over 0.5 m²:
- lux = 1 lumen / 0.5 m² = 2 lux
Conversion Example
- Convert 5 lumens to lux on 2 m²:
- Divide 5 lumens by 2 m²
- 5 / 2 = 2.5 lux
- So, 5 lumens on 2 m² equals 2.5 lux
- Convert 10 lumens to lux on 5 m²:
- Divide 10 lumens by 5 m²
- 10 / 5 = 2 lux
- Thus, 10 lumens across 5 m² gives 2 lux
- Convert 3 lumens to lux on 1.5 m²:
- Divide 3 lumens by 1.5 m²
- 3 / 1.5 = 2 lux
- The illuminance is 2 lux
- Convert 8 lumens to lux on 4 m²:
- 8 lumens ÷ 4 m² = 2 lux
- Meaning 8 lumens spread over 4 m² results in 2 lux
Conversion Chart
| Lumen | Lux (on 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 |
The chart shows lumen values and their equivalent lux values assuming the light hits an area of 1 square meter. To use the chart for other areas, divide the lumen value by the area in square meters to get lux.
Related Conversion Questions
- How many lux does 1 lumen produce on a 1 square meter surface?
- What’s the difference between lumen and lux when converting 1 lumen?
- Can 1 lumen equal 1 lux in all lighting conditions?
- How to calculate lux from 1 lumen if the surface area changes?
- Does 1 lumen always convert directly to 1 lux?
- What area is needed for 1 lumen to produce exactly 1 lux?
- How does distance affect lux value from 1 lumen source?
Conversion Definitions
Lumen: Lumen is a unit measuring the total quantity of visible light emitted by a source in all directions per second. It quantifies brightness as perceived by the human eye, combining intensity and spread, and it helps compare light output from bulbs or LEDs.
Lux: Lux measures illuminance, the amount of visible light falling on a surface area of one square meter. Unlike lumen, lux accounts for area, representing how bright the surface will appear, which is important for lighting design and eye comfort.
Conversion FAQs
Why does converting lumens to lux need surface area?
Because lumens measure total light output, while lux measures light per unit area. Without knowing the surface size, you can’t find how intense the light is at a given spot. The same lumens spread over larger area means less lux, and vice versa.
Can lux value be negative like lumens?
No, lux can’t be negative because it represents brightness on a surface. Negative lumens or lux don’t physically exist; negative values might appear in calculations or data errors but have no real lighting meaning.
Is 1 lumen always equal 1 lux?
Only if the 1 lumen is evenly spread over exactly 1 square meter. If the area changes, the lux value changes too. So 1 lumen equals 1 lux only at 1 m².
How does distance between light source and surface affect lux?
Lux decreases as distance increases because the same lumens spread over larger area. The illuminance follows inverse square law, so doubling distance reduces lux by four times.
What practical uses does converting lumen to lux have?
It helps in lighting design, determining how bright a room or surface will be based on light source output and room size. Knowing lux ensures comfortable, efficient lighting for workplaces, homes, and outdoor areas.
Last Updated : 04 July, 2025
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Sandeep Bhandari holds a Bachelor of Engineering in Computers from Thapar University (2006). He has 20 years of experience in the technology field. He has a keen interest in various technical fields, including database systems, computer networks, and programming. You can read more about him on his bio page.