Elara Bennett1 lux equals 1 lumen per square meter (lm/m²) on a surface. So, converting 1 lux to lumen depends on the area illuminated, but for 1 square meter, 1 lux equals exactly 1 lumen.
Lux measures illuminance, which is how much luminous flux hits a surface area, while lumen measures total luminous flux emitted. To convert lux to lumen, you multiply lux by the area in square meters. For 1 lux over 1 m², the lumen output is 1.
Conversion Tool
Result in lumen:
Conversion Formula
The formula to convert lux (lx) to lumen (lm) depends on the illuminated surface area. Lux is lumen per square meter, so the formula is:
Lumen (lm) = Lux (lx) × Area (m²)
This works because lux quantifies luminous flux per unit area — converting back to total luminous flux requires multiplying by the area illuminated. If you have 1 lux over 1 square meter, the lumen is 1 × 1 = 1 lm.
For example, if you have 10 lux over 2 square meters:
- Multiply: 10 lx × 2 m² = 20 lm
- The total luminous flux incident is 20 lumens.
Conversion Example
- Example 1: 5 lux over 3 m²
- Multiply 5 lx by 3 m²
- 5 × 3 = 15 lumens
- The total luminous flux is 15 lm.
- Example 2: 12 lux over 0.5 m²
- 12 lx × 0.5 m² = 6 lm
- So, 6 lumens total on that surface.
- Example 3: 20 lux over 4 m²
- 20 × 4 = 80 lumens
- The total luminous flux is 80 lm.
- Example 4: 0.1 lux over 10 m²
- 0.1 × 10 = 1 lumen
- The surface receives 1 lm in total.
Conversion Chart
| Lux (lx) | Lumen (lm) for 1 m² area |
|---|---|
| -24.0 | -24.0 |
| -20.0 | -20.0 |
| -16.0 | -16.0 |
| -12.0 | -12.0 |
| -8.0 | -8.0 |
| -4.0 | -4.0 |
| 0.0 | 0.0 |
| 4.0 | 4.0 |
| 8.0 | 8.0 |
| 12.0 | 12.0 |
| 16.0 | 16.0 |
| 20.0 | 20.0 |
| 24.0 | 24.0 |
| 26.0 | 26.0 |
The chart above shows lux values converted to lumens assuming the illuminated area is 1 square meter. To use it, find the lux value, then look under lumen column to see total luminous flux on 1 m².
Related Conversion Questions
- How do I convert 1 lux to lumens for a 2 square meter area?
- If I have 1 lux on a 0.5 m² surface, how many lumens does that equal?
- What is the lumen value for 1 lux lighting a a 10 m² room?
- Can 1 lux be directly equal to 1 lumen without knowing area?
- How many lumens correspond to 1 lux over a 3 square meter area?
- Is the conversion from lux to lumen linear at 1 lux?
- How to calculate lumens from 1 lux if area changes?
Conversion Definitions
Lux: Lux is a unit measuring illuminance, or the amount of luminous flux hitting a surface per square meter. It quantifies how bright a surface appears under a light source, accounting for both intensity and area illuminated, useful for lighting design and safety standards.
Lumen: Lumen measures total luminous flux emitted by a light source. It tells how much visible light is produced in all directions combined, important for rating brightness of bulbs and lamps independent of distance or surface area illuminated.
Conversion FAQs
Does converting 1 lux to lumen always require knowing the area?
Yes, because lux is a measure of luminous flux per square meter, the surface area illuminated is needed to find total lumens. Without area, you only know flux density, not total flux. For 1 m², 1 lux equals 1 lumen, but for other areas, multiply by the square meters.
Can lux be negative when converting to lumens?
Lux and lumen measure physical quantities of light, which can’t be negative. Negative lux values are non-physical and likely errors in measurement or input. If negative lux shows up, conversion to lumen should not be done until corrected.
Why is the lumen value dependent on area when converting from lux?
Lux measures light intensity per area, while lumens total light output. So, if light is spread over a larger area, lux decreases but total lumens stay same. To convert from lux to lumen, multiply by the surface area to capture total light hitting that surface.
Is the conversion between lux and lumen linear?
Yes, the relationship is linear. Doubling the area doubles the lumens for a given lux value. Similarly, doubling lux while keeping area constant doubles lumens. The direct multiplication formula ensures proportional conversion without nonlinear effects.
How accurate is the lux to lumen conversion for real-world lighting?
The conversion assumes uniform light distribution over the area. In reality, light may vary across surfaces, and reflections or angles affect measurements. For practical uses, the calculation gives an estimate, but precise measurement requires specialized instruments and consideration of geometry.
