Watts to Lumens Calculator

Lumens measure the brightness of a light, while watts measure energy consumption — the Watts to Lumens Calculator converts between the two so you can compare bulbs and choose the right brightness for any space. Enter your bulb's power in watts and select your lamp type (LED, CFL, halogen, incandescent, or fluorescent tube) to get the luminous flux in lumens. Secondary outputs include the luminous efficacy used in the calculation and a brightness category for your result.

W

Enter the electrical power consumption

lm/W

Only used when Custom Efficacy is selected

Results

Luminous Flux

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Luminous Efficacy Used

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Brightness Category

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Frequently Asked Questions

How do you calculate lumens from watts?

Lumens are calculated by multiplying watts by the luminous efficacy (lm/W) of the lamp type. The formula is: Lumens = Watts × Luminous Efficacy. Different lamp types have different efficacy ratings.

What is luminous efficacy and why does it matter?

Luminous efficacy measures how efficiently a light source converts electrical power into visible light, expressed in lumens per watt (lm/W). Higher efficacy means more light output per watt consumed, making the lamp more energy efficient.

Which lamp type is most energy efficient?

LED lamps are the most energy efficient, typically producing 80-100 lumens per watt. They're followed by fluorescent tubes (60-100 lm/W), CFL bulbs (50-70 lm/W), halogen (15-25 lm/W), and incandescent bulbs (10-17 lm/W).

How many lumens do I need for different rooms?

Lighting needs vary by room: living rooms typically need 1,500-3,000 lumens, bedrooms 2,000-4,000 lumens, kitchens 5,000-10,000 lumens, and bathrooms 4,000-8,000 lumens. Consider room size and activities performed.

Can I use this calculator for any type of light bulb?

Yes, this calculator works for all common lamp types including LED, CFL, halogen, incandescent, and fluorescent tubes. You can also enter a custom luminous efficacy value for specialty lighting.

What's the difference between watts and lumens?

Watts measure electrical power consumption, while lumens measure light output or brightness. Two bulbs with the same wattage can produce different amounts of light depending on their efficiency (luminous efficacy).