Lumen to Watt Calculator
Convert lumens to watts with step-by-step calculations. Perfect for energy calculations, LED specifications, and lighting efficiency analysis.
Luminous Flux to Power Converter
Common Lumen to Watt Conversions
Click on these links to see instant conversions with common values:
Understanding Lumen to Watt Conversion
Converting lumens to watts requires understanding luminous efficacy - how efficiently a light source converts electrical power into visible light. This conversion is essential for energy calculations and comparing different lighting technologies.
Conversion Formula
Where:
• watts = electrical power consumed
• lumens = luminous flux (total light output)
• luminous efficacy = efficiency rating (lm/W)
Key Concepts
- Lumens (lm): Total amount of visible light emitted by a source
- Watts (W): Electrical power consumed by the light source
- Luminous Efficacy (lm/W): Efficiency of converting electricity to light
- Energy Efficiency: Higher lm/W means less power needed for same light output
Power Requirements by Technology
| Light Output | Incandescent | Halogen | CFL | LED |
|---|---|---|---|---|
| 450 lm (40W equiv.) | 40W | 29W | 9W | 5W |
| 800 lm (60W equiv.) | 60W | 43W | 14W | 8W |
| 1100 lm (75W equiv.) | 75W | 53W | 18W | 11W |
| 1600 lm (100W equiv.) | 100W | 72W | 23W | 16W |
| 2600 lm (150W equiv.) | 150W | 116W | 38W | 25W |
Frequently Asked Questions
How do you convert lumens to watts?
Divide lumens by luminous efficacy (lm/W). For example: 800 lm ÷ 100 lm/W = 8W. The efficacy depends on the light source technology and efficiency.
Why can't you directly convert lumens to watts?
Lumens measure light output while watts measure power consumption. The conversion requires knowing the light source's efficiency (luminous efficacy), which varies significantly by technology.
What affects the lumens per watt ratio?
Light source technology is the main factor. LEDs are most efficient (80-200+ lm/W), followed by CFLs (50-70 lm/W), halogen (16-24 lm/W), and incandescent bulbs (10-17 lm/W).