Watts to Lux Calculator

What are Watts and Lux?

Watts (W) is a unit of power that measures the rate of energy transfer. In lighting, it represents the amount of electrical power consumed by a light source. Lux (lx) is the SI unit of illuminance, which measures the amount of light that falls on a surface area.

The Watts to Lux Formula

The conversion from watts to lux involves two steps:

1. Convert watts to lumens: \[\text{Lumens} = \text{Watts} \times \text{Efficacy}\] Where efficacy is measured in lumens per watt (lm/W).
2. Convert lumens to lux: \[\text{Lux} = \frac{\text{Lumens}}{\text{Surface Area}}\] Where surface area is measured in square meters (m²).

Combining these steps, we get:

\[\text{Lux} = \frac{\text{Watts} \times \text{Efficacy}}{\text{Surface Area}}\]

Where:

• Lux (lx) = Illuminance
• Watts (W) = Power of the light source
• Efficacy (lm/W) = Luminous efficacy of the light source
• Surface Area (m²) = Area illuminated by the light source

Step-by-Step Watts to Lux Calculation

1. Identify the power of the light source in watts (W).
2. Determine the luminous efficacy of the light source in lumens per watt (lm/W).
3. Measure or calculate the surface area being illuminated in square meters (m²).
4. Multiply the watts by the efficacy to get lumens.
5. Divide the lumens by the surface area to get lux.

Example Calculation

Let's calculate the illuminance for a 100W LED light with an efficacy of 100 lm/W, illuminating an area of 10 m²:

1. Power = 100 W
2. Efficacy = 100 lm/W
3. Surface Area = 10 m²
4. Lumens = 100 W × 100 lm/W = 10,000 lm
5. Lux = 10,000 lm ÷ 10 m² = 1,000 lx

Visual Representation

This diagram illustrates how a 100W LED light source with an efficacy of 100 lm/W produces an illuminance of 1,000 lux over a surface area of 10 m². The red point represents the light source, and the yellow circle shows the illuminated area.