What is Lumen

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When you buy bulbs and light fixture, you may find the word “lumen” many times. What is lumen?

The lumens definition is: “Luminous flux emitted in unit solid angle (steradian) by a uniform point source having a luminous intensity of 1 candela. Equivalent definition. Luminous flux of a beam of monochromatic radiation whose frequency is 540 × 1012 hertz and whose radiant flux is 1/683 watt..”

In short…
Lumens equals brightness!

Why not measure in watts?
Well, watts measure energy use, not light output. Therefore with the focus of LEDs being energy efficiency, we can no longer rely on wattage to indicate how bright a bulb is. An LED bulb will use less energy to produce the same brightness as a less efficient incandescent bulb.
See how to measure lumens in this chart

If you used to buy this in incandescent Look for this much light in lumens LED (most efficient) CFL (more efficient) Halogen (more efficient incandescent)
100 W 1600 < 22 W <26 W <72 W
75 W 1100 < 20 W <23 W <53 W
60 W 800 <12 W <15 W <43 W
40 W 450 <9 W <11 W <29 W

Lumens vs Watts: Output and wattages based on most common products available for each medium screw base light bulb. Actual light output may vary by product.

Use the chart to determine exactly how many lumens are in a watt and vice versa. This should provide you with a good understanding of how bright 120 lumens is vs. a fixture with 5000 lumens. Anyway, some manufacturers may exaggerate their product’s lumen value. For example, a flashlight written with 1000 lm, the real value could be only 200 lm.

How can we know the lumen value? You can get this information on the package of all our bulbs and lamps. Just remember, Lumens equals brightness, but lumen is not the only factor to influence brightness, such as the beam’s angle and lighting distance.

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