What is the Difference Between Lumens and Wattage?

What is the Difference Between Lumens and Wattage?

The traditional lighting concept that the higher the wattage of the lamp, the brighter the lamp, we all like high-wattage lights, but the era of LED lights, it has changed this traditional way of choosing lighting, choosing LED light fixtures not only paying attention to the power of the lamp, but also to pay attention to the brightness of the lamp to meet the requirements, as well as the LED lights energy-saving and environmentally friendly features.

When we usually buy home lights, we often use "wattage" to judge the brightness of the lamps, and the reference data on the packaging of lamps is also mostly based on wattage. But in recent years, the U.S. Federal Trade Commission proposed that all light bulb packaging reflect the brightness of the lumens (luminous flux units) in the forefront. This means that, in the future, the wattage will no longer be the standard for measuring the illumination of light bulbs.

Although luminous flux is the most commonly used physical quantity in the lighting industry, for more people, "wattage" may be more familiar than luminous flux, what is the difference between them?

First of all, it must be clear that lumens and watts are both used to indicate the "quantity of light" unit.

1. What is wattage?

Wattage is the unit of power, abbreviated as W, more commonly used in everyday life as a unit of kilowatt.

Power is the work done by the current per unit of time is called electrical power, is used to express the consumption of electrical energy in fast and slow physical quantity. As a physical quantity that indicates how fast the current does its work, the size of an appliance's power is numerically equal to the amount of electrical energy it consumes in 1 second.

2. What is lumen?

Lumen is a unit of luminous flux, abbreviated as lm, which simply means the luminance of a candle's light beyond one meter.

Luminous flux refers to the radiant power perceived by the human eye, which is equal to the product of the radiant energy of a certain wavelength per unit of time and the relative visibility of that wavelength. Because the human eye is to different wavelengths of light, the relative visibility of different wavelengths of light is different, so the luminous flux is not equal when the radiation power of different wavelengths of light is equal.

This "bright" feeling in photometry is called luminous flux, "bright" then luminous flux, "dark" then luminous flux is small, the unit of measuring the size of the luminous flux is called lumens. In other words, the number of lumens of light is large, the number of lumens of dark is small.

3. How do we convert lumens and wattage?

Luminous flux (lumens) = 683 x luminous efficiency x radiant flux (watts) 

In the case of LED lamps, it is now generally 50-70 lm/W, incandescent lamps are 10-15 lm/W, and energy-saving lamps 50-80 lm/W.

There will be variability in the data because there is not yet the same standard for LED lighting manufacturing parameters around the world, and each company has different indicators.

How do we convert lumens and wattage

Therefore, after understanding the difference between wattage and lumens, you can change the idea of buying incandescent lights in the past and choose the best LED lights to buy in the right way.


1. How many lumens is a LED floodlight?

Take ONFORU's LED floodlights as an example, the common floodlight lumens, and the corresponding wattage is as follows:

Items Wattage Lumens 
50W 4500lm
100W 10000lm
150W 12000lm
200W 20000lm

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