Lux vs Lumens: What You Must Know When Choosing LED lights

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Lux vs Lumens_ What You Must Know When Choosing LED lights

Do you really know the meaning of terms like lumens and lux when choosing LED lights? Are you still using the wattage of lights to determine whether they are bright or not? If you are a little confused about these terms, take 1-2 minutes to read this passage about Lux vs Lumens so that you can make a wiser choice next time!

Definition of Lumens

Lumens are units of luminous flux that represent the total emitted luminous flux produced by one candle at a solid angle. The SI unit of light intensity is the candela. Given that the solid angle of the entire sphere is 4π, a standard candle emits 4π (about 12.56) lumens. The higher the lumen value, the brighter the light seems.

Lumens vs Watt

Light intensity (unit: lumens) = Watt * Luminous efficiency (unit: lumens/Watt). Luminous efficiency vary for different light sources. Thus, watts is not the suitable unit of measurement for brightness. From the initial incandescent bulb to the modern LED lamp, the luminous efficiency of light sources has steadily improved as lighting technology advances. For instance, a 60W incandescent bulb, a 15W fluorescent bulb, and a 9W LED bulb all have approximately the same lumen output. The improvement of luminous efficiency is also one of the reasons for LED lights becoming the main light source for street lighting.
The sensitivity of the human eye to various light colors varies. The yellow-green 555nm light has significantly more lumens and seems brighter than the red 650nm light at the same watt.


How is lumen measured?

The integrating sphere is the standard lumen measurement tool. To ensure that there is an even distribution of light throughout the ball, the light source is positioned in its center. One side of the ball has a photometer that records the amount of light that reaches a specific spot on the ball. You may adjust this photometer to detect light intensity at various spots around the sphere. The total amount of light received over the ball’s surface can be determined by measuring the light intensity at various spots within the ball. The lumen value of the light source is this entire amount of light.

Lux vs Lumens

The same lumen value may be appropriate for a small space but insufficient for a large room. Because of this, Lux is typically used to define the level of brightness needed in various application contexts. The uniformly distributed light flux of one lumen per square meter is known as lux. The area’s light intensity increases with the lux value. 1 Lux is different from 1 lumens because it accounts for the dispersed area of light flux.

How bright is 1000 lux?

On a cloudy day, the amount of light outdoors is approximately 1000 lux. At noon, the direct sunlight can exceed 100,000 lux. The usual range of indoor lighting is 100–500 lux. The lighting in spaces that need more light, like libraries or offices, can be kept between 300 and 500 lux. Family living rooms often have lower lighting, between 100 and 300 lux.


All in all, when you are choosing LED lights, look for lumens instead of watt. Most manufacturers provide information about lumens on the specification of the product. This lumen value is for the average size of certain application settings, because the size of each customer’s space is different. If your place has an average size, you can judge by lumens. You can also figure out the light intensity (unit: lux) by dividing the luminous flux (unit: lumens) by the area size. Then compared the lux level with the standards promoted by associations like IESNA to see if the lights you want to buy are suitable or not. If you are not sure, you can contact experts from Casyoo to get to know more standards for different spaces!

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Victor Guo

Victor Guo

Lead electrical engineer with 17+ years of experience designing electrical street lighting systems, monitoring electrical-related work at site, and discussing proposal and lighting implementation options. Bachelor’s degree in electrical engineering. Knowledgeable in LED lighting design, project management, safety and compliance.
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