Why do you need luminous efficacy to convert lux to watts?

Luminous efficacy (lm/W) shows how efficiently a light source converts electricity to light. Different technologies have different efficiencies, affecting power consumption for the same light output.

Lux to Watt Calculator

Q: How do you convert lux to watts?

To convert lux to watts, use the formula: watts = (lux × distance²) ÷ luminous efficacy. First calculate lumens from lux and area, then divide by efficacy to get power consumption.

Q: What information is needed for lux to watt conversion?

You need illuminance (lux), distance from light source (meters), and luminous efficacy of the light source (lm/W). The calculation involves converting lux to lumens, then lumens to watts.

Convert lux to watts with step-by-step calculations. Perfect for energy calculations, lighting design, and power consumption analysis.

Illuminance to Power Converter

Lux (lx):

Distance (m):

Efficacy (lm/W):

Light Type:

1m Distance 2m Distance 3m Distance LED (100 lm/W)

Common Lux to Watt Conversions

Click on these links to see instant conversions with common values:

Understanding Lux to Watt Conversion

Converting lux to watts requires understanding both the inverse square law and luminous efficacy. This conversion is essential for determining power consumption needed to achieve specific illuminance levels.

Conversion Formula

watts = (lux × distance²) ÷ luminous efficacy

Step 1: lumens = lux × distance² (m²)
Step 2: watts = lumens ÷ efficacy (lm/W)

Where:
• watts = electrical power consumed
• lux = illuminance (light per unit area)
• distance = distance from source (meters)
• efficacy = luminous efficacy (lm/W)

Key Concepts

Lux (lx): Illuminance - the amount of light falling on a surface per unit area
Watts (W): Electrical power consumed by the light source
Distance Factor: Light spreads over larger areas as distance increases
Luminous Efficacy: How efficiently electricity is converted to visible light

Power Requirements for Common Illuminance Levels

Illuminance	Application	LED Power (2m)	CFL Power (2m)	Incandescent (2m)
50 lux	Ambient lighting	2W	3.3W	16.7W
200 lux	General lighting	8W	13.3W	66.7W
300 lux	Office work	12W	20W	100W
500 lux	Task lighting	20W	33.3W	166.7W
750 lux	Detailed work	30W	50W	250W

Frequently Asked Questions

How do you convert lux to watts?

First calculate lumens from lux and distance: lumens = lux × distance². Then divide by luminous efficacy: watts = lumens ÷ efficacy. Both steps are needed for accurate conversion.

Why do you need luminous efficacy for lux to watt conversion?

Luminous efficacy shows how efficiently a light source converts electricity to light. Different technologies (LED, CFL, incandescent) have different efficiencies, affecting power consumption.

What information is needed for lux to watt conversion?

You need illuminance (lux), distance from the light source (meters), and the luminous efficacy of the specific light source technology (lm/W).