Convert brightness in lumens to power in watts for different bulb types. Enter the lumens and, if you like, the efficacy of your own lamp. Free, private, and runs entirely in your browser.
Watts equal lumens divided by the luminous efficacy of the lamp, measured in lumens per watt. Different technologies have very different efficacies, so the same brightness needs fewer watts from an LED than from an incandescent bulb.
How many watts is 800 lumens? About 60 W for an incandescent bulb, 44 W for halogen, 13 W for a CFL and roughly 9 W for an LED.
Is there an exact conversion? No. Lumens measure light output and watts measure power use, so the link depends on the lamp efficacy.
A room needs a bulb that gives 800 lumens. At 13.3 lm/W an incandescent bulb needs 800 ÷ 13.3 ≈ 60 W. A CFL at 60 lm/W needs about 13.3 W, and an LED at 90 lm/W needs about 8.9 W.
How many lumens does a room need? Common guidance is about 10 to 20 lumens per square foot, depending on the use of the room.
Does color temperature change lumens? Not directly, but a warm or cool bulb can look brighter or dimmer to the eye.
The lumen is defined as the light emitted in one steradian by a source of one candela. For decades bulbs were sold by watts, because incandescent efficiency was similar between brands. As the EU phased out most incandescent bulbs between 2009 and 2012 and the US introduced Lighting Facts labels in 2011, packaging switched to lumens so that shoppers could compare different technologies.
Use this calculator to choose a replacement bulb, to estimate the savings from switching to LED, or to size lighting for a room. For example, replacing a 60 W incandescent with a 9 W LED saves about 51 W per hour of use. The electricity calculator can turn that into cost.
What is luminous efficacy? The light output per unit of power, in lumens per watt. Higher is more efficient.
How do I convert watts back to lumens? Multiply the watts by the efficacy of the lamp.