How to Use Lumen to Watt Converter
The Lumen to Watt Converter estimates the electrical power needed to produce a target light output with different bulb technologies. This helps when replacing old watt-based bulbs with modern lamps where brightness is printed in lumens.
- Enter lumens — printed on every modern bulb box.
- Pick a light source — LED, halogen, incandescent, CFL or custom.
- Use custom efficacy if you have a specific lm/W datasheet value.
- Read watts needed for that source.
- Compare with the LED equivalent to estimate savings.
Formula & Theory — Lumen to Watt Converter
The Lumen to Watt Converter divides desired lumens by luminous efficacy. Higher efficacy means more visible light per watt and therefore lower power consumption for the same brightness.
watts = lumens / efficacy_lmPerW
LED efficacy ≈ 90, CFL ≈ 60, halogen ≈ 20, incandescent ≈ 13| Source | Typical efficacy used |
|---|---|
| LED | 90 lm/W |
| CFL | 60 lm/W |
| Halogen | 20 lm/W |
| Incandescent | 13 lm/W |
Assumptions and Limits
Efficacy varies by lamp quality, color temperature, driver efficiency, dimming and beam angle. Lumens measure total light output, not how focused the beam is. For task lighting, also check fixture distribution, CRI and glare control.
Use Cases for Lumen to Watt Converter
The Lumen to Watt Converter is useful for:
- Bulb replacements — Find a lower-watt LED with the same brightness.
- Remodel fixture sizing — Estimate total load before choosing circuits.
- Energy savings — Compare incandescent, halogen, CFL and LED power.
- Custom products — Use a datasheet lm/W value for specialty lamps.
When buying bulbs, choose by lumens first, then check wattage, color temperature and fixture compatibility.