1 Lumen to Lux – Answer with Formula

1 lumen equals 1 lux when the light is uniformly spread over an area of 1 square meter.

Lumen measures the total quantity of visible light emitted by a source, whereas lux measures the illumination on a surface area. Since lux is lumens per square meter, 1 lumen shining on 1 square meter equals 1 lux.

Conversion Tool

Conversion Formula

The formula to convert lumen to lux depends on the area illuminated. Lux is defined as lumens per square meter (lm/m²). So:

lux = lumens ÷ area (in square meters)

This formula works because lumen quantify the total light output, but lux measures how intense that light is on a surface. The same lumen value will produce different lux values if spread over different areas.

Example:

• If you have 1 lumen illuminating 1 square meter, lux = 1 ÷ 1 = 1 lux.
• If 1 lumen covers 0.5 m², lux = 1 ÷ 0.5 = 2 lux.

Conversion Example

• 5 lumens on 1 m²:
  • Input lumens: 5
  • Area: 1 m²
  • lux = 5 ÷ 1 = 5 lux
• 10 lumens on 2 m²:
  • Input lumens: 10
  • Area: 2 m²
  • lux = 10 ÷ 2 = 5 lux
• 50 lumens on 5 m²:
  • Input lumens: 50
  • Area: 5 m²
  • lux = 50 ÷ 5 = 10 lux
• 0.5 lumens on 0.25 m²:
  • Input lumens: 0.5
  • Area: 0.25 m²
  • lux = 0.5 ÷ 0.25 = 2 lux

Conversion Chart

The following chart shows lumen values from -24.0 to 26.0 converted to lux, assuming the light covers 1 square meter. Negative lumen values are physically unrealistic but included for completeness.

To use the chart, find the lumen value in the left column, then read across to find it’s corresponding lux value, assuming the illumination area is one square meter.

Related Conversion Questions

• How many lux does 1 lumen produce over 0.5 square meters?
• What is the lux value of 1 lumen on a 2 square meter surface?
• Can 1 lumen equal 1 lux in all situations?
• How do I calculate lux from 1 lumen if the area is unknown?
• Is 1 lumen always brighter than 1 lux?
• What changes lux value more, lumen or area?
• How does distance affect converting 1 lumen to lux?

Conversion Definitions

Lumen: Lumen measures the total amount of visible light emitted by a source in all directions. It quantifies light power as perceived by the human eye, combining intensity and the area illuminated. Lumen is a photometric unit used to express brightness output.

Lux: Lux is the measure of illumination on a surface area, representing lumens per square meter. It indicates how much light lands on a specific area, showing the intensity of light that the human eye perceives on surfaces in practical environments.

Conversion FAQs

Can lux be higher than lumens?

Yes, lux can be higher than lumens if the same amount of lumens is concentrated on a smaller area. Since lux equals lumens divided by area, reducing the illuminated surface causes lux to increase. Lumens measure total light output, lux shows light intensity on surfaces.

Does distance between light source and surface affect lux?

Distance strongly affects lux because as light spreads over a larger area at greater distances, the lux value decreases. Though lumens remain constant, lux decreases by the square of the distance, following the inverse square law for light intensity.

Is it possible to convert lumen to lux without knowing area?

No, converting lumen to lux always requires knowing the area illuminated. Lux depends on how lumens spread over an area. Without area, the lux value can’t be calculated, only the total light output in lumens can be known.

Why can lumen be negative in some tables?

Negative lumen values are not physically possible; they sometimes appear in charts for mathematical completeness or error checking. Actual light output cannot be less than zero because it represents emitted light quantity.

How does surface reflectivity affect lux?

Surface reflectivity changes perceived brightness but doesn’t alter lux directly. Lux measures incident light on a surface; reflective surfaces may appear brighter, but the lux value remains the same unless additional light is emitted or reflected back.