Lamp Brightness Converter

Modern light bulbs are rated in lumens (brightness) rather than watts (energy consumption). This converter helps you find equivalent brightness across different bulb technologies.

What are lumens and watts?

• Lumens (lm): A measure of the total amount of visible light emitted by a source. More lumens = brighter light.
• Watts (W): A measure of energy consumption. More watts = more electricity used.
• Old incandescent bulbs wasted most energy as heat, so watts roughly indicated brightness. Modern LEDs produce the same brightness using far fewer watts.

Brightness equivalence table:

Approximate efficiency (lumens per watt):

• Incandescent: 10-17 lm/W (very inefficient, mostly heat)
• Halogen: 15-25 lm/W (slightly better than incandescent)
• CFL (compact fluorescent): 50-70 lm/W (good efficiency)
• LED: 80-150 lm/W (excellent efficiency, best value)

How the conversion actually works, and why one number will not do it:

Incandescent efficacy is not a constant. Run the table above and it climbs steadily: a 40 W bulb manages 11.3 lumens per watt, a 60 W bulb 13.3, a 100 W bulb 16.0. Bigger filaments run hotter, and hotter filaments push more of their output into visible light rather than infrared. So any converter using a single figure has to be wrong somewhere. A flat 14 lm/W, which this page used to use, turns 1,600 lumens into a 114 W bulb when the table right above it says 100 W.

The calculator therefore interpolates along the equivalence table itself, and the answers it gives match the rows you can read for yourself. Outside the table’s range it falls back to the efficacy of the nearest end, which is the honest thing to do with an extrapolation.

• LED watts from lumens: W = lm / 90 (a fair average; good LEDs reach 100 and better)
• CFL watts from lumens: W = lm / 60 (approximate average)

Practical tips for choosing bulbs:

• To replace a 60W incandescent, look for an LED bulb rated at 800 lumens.
• LED bulbs last 15,000-50,000 hours compared to 1,000 hours for incandescent bulbs.
• CFL bulbs contain small amounts of mercury and should be recycled properly, not thrown in regular trash.
• Color temperature (measured in Kelvin) is separate from brightness. A 2700K bulb gives warm yellowish light, while 5000K gives cool daylight-white light.
• Dimmer switches require dimmable LED bulbs specifically labeled as compatible.