Lumens to Watts Converter
Convert lumens to approximate watts, or watts to lumens, for LED, CFL, halogen and incandescent bulbs, using typical efficacy figures. Includes a worked example.
Results
Watts (approx.)
- Lumens (approx.)
- 800 lm
- Assumed efficacy
- 90 lm/W
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Educational estimates · not financial advice · free, no signup
Formula / how it works
Rough efficacy (lm/W): LED ≈ 90, CFL ≈ 60, halogen ≈ 20, incandescent ≈ 15. Watts ≈ lumens ÷ efficacy.
Detailed guide
What it is, how to use it, how to read the numbers, common mistakes, a worked example, formulas, and FAQs.
What this calculator is
Lumens measure how much visible light a bulb produces, while watts measure the electrical power it uses. For old incandescent bulbs the two were tightly linked, which is why people still shop by watts. Modern LEDs produce far more light per watt, so a bulb that gives the light of a traditional 60 W lamp may draw under 10 W. This converter applies typical efficacy figures for each lamp type to estimate watts from lumens, or lumens from watts. It is meant for planning replacements and comparing running costs, not for photometric design. Actual efficacy differs between models, so the numbers on the packaging take priority.
When to use / who it helps
- You are replacing an incandescent bulb with an LED and want a similar brightness.
- You know the lumens you want in a room and need the likely power draw.
- You are comparing running costs of different bulb types.
- You are reading a lamp spec in lumens and want a feel for it in watts.
- You are planning lighting for a space and need approximate power per fixture.
How to use
Steps
- Choose whether you are converting lumens to watts or watts to lumens.
- Enter the value; for example 800 lumens is typical of a household general-purpose bulb.
- Pick the lamp type so the right efficacy is used.
- Read the approximate result and the assumed lm/W.
- Compare two lamp types by changing only the type.
- Replace the estimate with the actual lumens and watts printed on the packaging when you have them.
How to interpret results
- A higher lm/W means more light for each watt; LEDs are far above incandescent bulbs.
- The result is an estimate based on a typical efficacy, not the rating of a specific product.
- Lumens describe light output; the colour temperature, beam angle and fixture affect how bright a room looks.
- Dimmable and smart bulbs may use slightly more standby power.
- Running cost scales with watts, not lumens, so a lower wattage for the same lumens saves energy.
Common mistakes & gotchas
- Assuming watts measure brightness for LEDs.
- Using the estimate instead of the efficacy printed on the package.
- Comparing lumens from different measuring conditions without checking.
- Ignoring the fixture, which can reduce delivered light.
- Forgetting that very cheap bulbs may fall below typical efficacy.
Worked example
Worked example — 800 lumens
- As an LED at about 90 lm/W: 800 ÷ 90 ≈ 8.9 W.
- As a CFL at about 60 lm/W: 800 ÷ 60 ≈ 13.3 W.
- As a halogen at about 20 lm/W: 800 ÷ 20 = 40 W.
- As an incandescent at about 15 lm/W: 800 ÷ 15 ≈ 53 W, close to the traditional 60 W bulb.
Result: 800 lumens needs roughly 9 W as an LED versus about 53 W as an incandescent bulb.
To load the form's own demo values, tap Try example above the Calculate button.
How to calculate / formula
Rough efficacy (lm/W): LED ≈ 90, CFL ≈ 60, halogen ≈ 20, incandescent ≈ 15. Watts ≈ lumens ÷ efficacy.
Frequently asked questions
How many lumens is a 60 watt bulb?
A traditional 60 W incandescent bulb produces roughly 800 lumens, although packaging gives the exact figure.
How many watts is 800 lumens?
About 9 W for an LED, 13 W for a CFL and 53 W for an incandescent bulb, using typical efficacy values.
Are lumens or watts a measure of brightness?
Lumens measure light output. Watts measure power consumption.
Why do LEDs use fewer watts?
They convert more of the electrical energy into visible light and waste less as heat.
Is this exact for my bulb?
No. It uses typical efficacy values. Check the lumens and watts on the packaging.
How do I choose a bulb for a room?
Compare lumens, then consider colour temperature and dimming. Choose the lowest wattage that gives the lumens you need.