15 Lumens to Lux – Answer with Formula

15 lumens corresponds to 15 lux when the light is spread evenly over an area of 1 square meter. In simple terms, if you have 15 lumens of luminous flux distributed across 1 square meter, the illuminance on that surface is 15 lux.

Lumens measure the total amount of visible light emitted by a source, whereas lux measures how much of that light falls on a given area. So converting lumens to lux depends on the area over which the lumens are spread, here we assume 1 square meter for direct conversion.

Conversion Tool

Conversion Formula

The formula to convert lumens (lm) to lux (lx) depends on the area (in square meters) over which the light is distributed. Lux is lumens divided by area:

lux = lumens / area

This formula works because lux measures illuminance, which is the luminous flux per unit area. Lumens counts total visible light output, but how bright it looks on a surface depends on how spread out it is.

For example, if 15 lumens spread evenly over 1 square meter:

• lux = 15 lm / 1 m² = 15 lx

If the same 15 lumens spread over 3 square meters:

• lux = 15 lm / 3 m² = 5 lx

So the smaller the area, the higher the lux for same lumens.

Conversion Example

• Convert 30 lumens to lux over 2 m²:
  • Calculate lux = 30 lm ÷ 2 m²
  • Result = 15 lx
  • This means 30 lumens spread over 2 square meters equals 15 lux illuminance.
• Convert 50 lumens to lux over 5 m²:
  • lux = 50 lm ÷ 5 m²
  • lux = 10 lx
  • More area means less lux for same lumens.
• Convert 100 lumens to lux over 10 m²:
  • lux = 100 lm ÷ 10 m²
  • lux = 10 lx
  • Illuminance decreases as light spreads over larger surface.
• Convert 20 lumens to lux over 0.5 m²:
  • lux = 20 lm ÷ 0.5 m²
  • lux = 40 lx
  • Smaller area causes higher lux value.

Conversion Chart

The chart shows lumens converted to lux, assuming the light spread across 1 square meter. Negative values or zero indicate no light or invalid situations but are included here for completeness. Use the chart for quick reference when converting values in this range.

Related Conversion Questions

• How many lux does 15 lumens produce on a 1 m² surface?
• What is the lux value if 15 lumens spread over 0.5 square meters?
• Can 15 lumens be converted to lux without knowing the area?
• Is 15 lumens equal to 15 lux in every situation?
• How does changing the area affect lux when having 15 lumens?
• What area would make 15 lumens equal to 30 lux?
• How to calculate lux from 15 lumens for different surfaces?

Conversion Definitions

Lumens: Lumens measure the total light output emitted by a source in all directions. It quantifies the perceived brightness of the light, regardless of direction or area illuminated. A higher lumens value means a brighter light source, but not necessarily higher brightness on a specific surface.

Lux: Lux measures the amount of light that falls on a surface per unit area, expressed as lumens per square meter. It tells how intense the illumination is on that surface. Lux considers both luminous flux and the size of the area being lit, providing a measure of illuminance.

Conversion FAQs

Can I convert lumens to lux without knowing the surface area?

No, converting lumens to lux requires knowing the area over which the light is spread because lux depends on luminous flux per unit area. Without area, you cannot get an accurate lux value from lumens alone.

What happens if lumens are spread unevenly on a surface?

Lux assumes uniform distribution of light over the area. If light is uneven, lux varies across the surface, making a single lux value less accurate. To measure actual lux, use a light meter at specific points.

Why can lux values be higher than lumens sometimes?

Lux can be higher than lumens only if the light is concentrated on a small area because lux = lumens ÷ area. Concentrating lumens into a smaller surface increases lux, even if the total lumens remain the same.

Is there a direct conversion for lumens to lux without area?

No direct conversion exists because lumens measure total light output, and lux measures illuminance on an area. The area size is essential for conversion, so you must have it to calculate lux from lumens.

How does distance affect the conversion of lumens to lux?

Lumens do not change with distance, but lux decreases as distance increases because the same lumens spread over a larger area. Lux reduces roughly with the square of the distance from the light source, affecting brightness perception.