Enter your lumens value and select a bulb type (Incandescent, Halogen, CFL, or LED) to find the equivalent wattage. The Lumens to Watts Calculator uses each bulb's luminous efficacy (lm/W) to convert brightness into power — so you can shop smarter and pick the right replacement bulb.
Power (Watts)
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Luminous Efficacy Used
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Bulb Type
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Watts measure electrical power consumption, while lumens measure the amount of visible light (brightness) a bulb produces. Historically, higher wattage meant a brighter bulb, but modern efficient bulbs like LEDs produce far more lumens per watt — so lumens are now the better measure of brightness.
The formula is: Power (W) = Luminous Flux (lm) ÷ Luminous Efficacy (lm/W). For example, an 800 lm LED bulb with an efficacy of 90 lm/W requires approximately 8.9 watts.
Lumens per watt (lm/W) is a measure of a bulb's luminous efficacy — how efficiently it converts electrical energy into light. A higher lm/W means more light for less power. LEDs typically achieve 80–100 lm/W, while incandescent bulbs manage only 10–18 lm/W.
It depends on the brightness (lumens) you need and the bulb type you're using. As a guide: a 60W incandescent equivalent produces about 800 lumens, which an LED can match with as little as 9 watts. Use this calculator to find the exact wattage for any lumen target and bulb type.
LEDs are the most energy-efficient choice, producing the most lumens per watt and lasting the longest. CFLs are also efficient but take time to warm up. Halogen bulbs are slightly more efficient than incandescent but still consume significantly more power than LEDs for the same brightness.
LED (Light Emitting Diode) technology converts a much higher proportion of electrical energy directly into light, with minimal energy lost as heat. Incandescent bulbs, by contrast, generate a lot of heat and only convert a small fraction of their energy into visible light.
This calculator converts lumens to watts. To go the other way, multiply the wattage by the bulb's luminous efficacy (lm/W). For example, a 10W LED at 90 lm/W produces 900 lumens. Many calculator sites also offer a dedicated Watts to Lumens calculator for the reverse conversion.
This calculator uses typical average values: Incandescent ≈ 15 lm/W, Halogen ≈ 20 lm/W, CFL ≈ 60 lm/W, and LED ≈ 90 lm/W. Actual values vary by manufacturer and model, so you can also enter a custom lm/W figure for greater accuracy.