Convert electrical power (watts) to illuminance (lux) using luminous efficacy and area in square meters.
Formula:
Lumens = Watts × Efficacy (lm/W)Lux = Lumens / Area (m²)The Watts to Lux Calculator is a powerful tool designed to help users estimate the illuminance (lux) produced by a light source based on its power consumption in watts. This conversion is especially helpful in architectural lighting design, interior planning, energy audits, and industrial installations where precise lighting levels are critical.
Watt (W) measures the power or energy consumption of a light source. It indicates how much electricity the source uses.
Lux (lx) is the unit of illuminance and refers to how much light (lumens) falls on a surface area (measured in lumens per square meter).
The conversion from watts to lux depends on the luminous efficacy of the light source and the area being illuminated. Here's the basic formula:
Lux = (Watts × Luminous Efficacy) / AreaWhere:
Suppose you have a 20-watt LED with an efficacy of 100 lm/W and it's lighting a 5 square meter area:
Lux = (20 × 100) / 5 = 2000 / 5 = 400 luxThis means the surface will receive an illuminance of 400 lux from the light source.
| Area | Recommended Lux |
|---|---|
| Living Room | 100–300 lx |
| Office Workspace | 300–500 lx |
| Retail Store | 500–1000 lx |
| Hospital Operating Room | 1000–1500 lx |
| Industrial Warehouse | 150–300 lx |
Converting watts to lux is essential for making energy-conscious lighting decisions. By accounting for both the light output (based on watts and efficacy) and the illuminated area, you can ensure that a space is neither under-lit nor over-lit. Use our Watts to Lux Calculator to determine the optimal illuminance for any environment.
The Watts to Lux Calculator is a powerful tool designed to help users estimate the illuminance (lux) produced by a light source based on its power consumption in watts. This conversion is especially helpful in architectural lighting design, interior planning, energy audits, and industrial installations where precise lighting levels are critical.
Watt (W) measures the power or energy consumption of a light source. It indicates how much electricity the source uses.
Lux (lx) is the unit of illuminance and refers to how much light (lumens) falls on a surface area (measured in lumens per square meter).
The conversion from watts to lux depends on the luminous efficacy of the light source and the area being illuminated. Here's the basic formula:
Lux = (Watts × Luminous Efficacy) / AreaWhere:
Suppose you have a 20-watt LED with an efficacy of 100 lm/W and it's lighting a 5 square meter area:
Lux = (20 × 100) / 5 = 2000 / 5 = 400 luxThis means the surface will receive an illuminance of 400 lux from the light source.
| Area | Recommended Lux |
|---|---|
| Living Room | 100–300 lx |
| Office Workspace | 300–500 lx |
| Retail Store | 500–1000 lx |
| Hospital Operating Room | 1000–1500 lx |
| Industrial Warehouse | 150–300 lx |
Professional lighting designers use lighting simulation software (like DIALux or Relux) to model lux distribution based on architectural plans, luminaire selection, and environmental factors. These tools use real IES data from manufacturers to achieve optimal accuracy.
A: No. Lux depends on how light spreads across a surface area. Without the area, the lux value can't be calculated accurately.
A: Not necessarily. Focus on luminous efficacy and proper light placement. A lower watt LED with high efficacy can outperform a higher watt incandescent.
A: Use fixtures with better optical design, adjust beam angles, or add reflective surfaces to bounce light more effectively.
A: Yes. It’s useful for street lights, stadiums, parks, and architectural lighting, provided you know the area and luminous efficacy.
The Watts to Lux Calculator bridges the gap between power consumption and practical illumination, helping users design smarter, more energy-efficient lighting systems. Whether you’re an engineer, architect, student, or homeowner, understanding this conversion ensures that your spaces are lit safely, effectively, and economically.