Lumens to Watts Calculator
Quickly convert light output and power draw for popular bulb types. Estimate energy usage and annual costs based on your lighting habits.
What are lumens?
Lumens measure light output. Modern packaging lists lumens so you can compare brightness across different bulb types.
| Bulb Type | Watts Needed | Yearly kWh | Yearly Cost |
|---|---|---|---|
Incandescent Traditional filament bulbs with the warmest glow but lowest efficiency. | 53.3 W | 77.9 | $14.02 |
Halogen Improved incandescent technology with slightly higher efficiency. | 40.0 W | 58.4 | $10.51 |
CFL Compact fluorescents that offer big efficiency gains with cooler light. | 13.3 W | 19.5 | $3.50 |
LED Highly efficient, long-lasting light-emitting diodes. | 8.9 W | 13.0 | $2.34 |
Tube Fluorescent Linear tube lighting common in offices and garages. | 11.4 W | 16.7 | $3.00 |
HID / Metal Halide High-intensity discharge lamps for exterior and industrial lighting. | 9.4 W | 13.7 | $2.47 |
How to Use This Calculator
Choose Your Conversion
Select whether you want to convert lumens to watts or watts to lumens, then pick the bulb technology you care about.
Enter Your Lighting Details
Type the lumen or watt rating, plus your typical hours of use and electricity price for accurate cost estimates.
Compare Technologies
Review the table to see how different bulbs deliver the same brightness with less power and lower annual costs.
Formula
Watts = Lumens ÷ Luminous Efficacy
Lumens = Watts × Luminous Efficacy
Annual kWh = (Watts × Hours per Day × 365) ÷ 1000
Example: 800 lumens ÷ 90 lm/W (LED) ≈ 8.9 watts, using 4 hours/day costs about $2.34 per year at $0.18/kWh.
Example: A 60 W incandescent bulb × 15 lm/W ≈ 900 lumens, consuming ~87.6 kWh annually if used 4 hours/day.
About This Calculator
Lighting labels focus on lumens, but retrofit decisions and breaker sizing still rely on watts. This tool bridges the gap so you can size fixtures, compare technologies, and forecast energy savings without guesswork.
When You Might Need It
- Upgrading bulbs: Find the LED wattage that matches your current brightness.
- Remodeling projects: Estimate lighting loads for room circuits or generators.
- Energy audits: Quantify savings from swapping older technologies.
- Photography and video: Balance light levels across fixtures with different outputs.
Tips for Accurate Results
- Check manufacturer datasheets—premium LEDs can exceed 110 lm/W.
- Use actual operating hours instead of estimates for commercial spaces.
- Adjust cost per kWh for peak vs off-peak billing or time-of-use plans.
- Remember dimmers change both lumens and watts—measure at typical settings.
Frequently Asked Questions
How accurate are the lumen-per-watt values?
They represent typical real-world ranges. Check the packaging or spec sheet for exact values—premium LEDs and fluorescents may be more efficient.
Why do LEDs need so few watts?
LEDs convert far more electrical power into visible light instead of heat. That's why a 10 W LED matches a 60 W incandescent.
Can I use this for dimmable fixtures?
Yes. Enter the brightness level (lumens) you want or the watt draw at your typical dimmer setting to compare energy use.
Does color temperature affect efficiency?
Only slightly. Warm LEDs are often a bit less efficient than cool white versions, but the difference is usually within 5–10%.