How to Convert Lumen to Watts – Lumen Watt Conversion Calculator

The days of selecting light bulbs based on wattage are long gone. Instead, with today’s contemporary LED bulbs, we must concentrate on lumens. But what is a lumen, exactly? We’ll go over that, and then you’ll be able to utilize our lumen watt conversion chart to get the proper LED bulb every time.

What is Watt (W)?

Watt & Lumen
Watt & Lumen

The watt (symbol: W) is a power or radiant flux measurement unit. It is defined as a derived unit of (in SI base units) 1 kgm2s3 or, equivalently, 1 joule per second in the International System of Units (SI). It is used to calculate the rate at which energy is transferred.

Every second, a one-watt lightbulb, for example, converts one joule of electrical energy into light energy (and some heat/sound), thus “eating” it. It’s a metric for determining how powerful an appliance is (appetite for joules).

Watts, named after James Watt, the inventor of the steam engine, are the units of power used to measure electricity. 

We pay for the number of watts we use when we pay our electric bill. A 60-watt bulb uses 60 watts of electricity to operate. Because we’ve been using 60-watt incandescent bulbs for so long, we’ve come to equate 60 watts with a certain amount of brightness.

But that’s no longer possible, thanks to LED technology, which generates greater light while consuming fewer watts. Lumens must be used instead.

What is Lumen (L)?

The lumen is defined as “a measure of the total “amount” of visible light emitted from a source in a specific beam or angle.” In other words, a lumen is a unit of brightness. Watts, on the other hand, does not. Watts is a unit of measurement for energy consumption rather than light output.

Regardless of efficiency or lighting technology, the lumen number can be used to compare the brightness of different lamps. When employing LED bulbs, the brightness in lumens is especially significant. You can use the Lumen Watt Calculator to compare the brightness of various light sources.

The stronger the light, the higher the lumens. All lighting manufacturers are now disclosing the number of lumens produced by each of their products. These lumen figures may be found on the Lighting Facts labels on all new LED bulb packaging.

It may take some time to adjust to utilizing lumens rather than watts, but it’s necessary for making the best lighting decisions.

Read more: Illuminance Calculator: All-to-know about Calculating Illuminance

What is Luminous Efficacy (Lumens/Watt)

What is Luminous Efficacy (Lumens_Watt)

The luminous effectiveness of a light source is a measurement of how successfully it produces visible light. It’s the lumens per watt (lm/w) ratio of luminous flux to power in the International System of Units (SI). Luminous efficacy peaks at 683 lumens per watt at 555 nm in the photopic range.

In actuality, the lumen is measured in power at 555 nm (with a frequency of 540 1012 Hz). Tungsten incandescent lamps had an effectiveness of roughly 15 lumens/watt in the old technology.

LEDs typically provide 70-100 lumens per watt. As a result, LEDs are around 5-6 times more efficient than incandescent bulbs at producing light. When choosing an LED bulb to replace an incandescent bulb, use this 5:1 or 6:1 ratio as a rough reference.

If you need to replace a 60-watt incandescent bulb with an LED bulb, divide 60 watts by 5 to get 12 watts, which is a good approximation.

However, because efficacy varies greatly from one manufacturer to the next, it’s essential to examine the Lighting Facts label and compare lumens. Also, a label will occasionally (but not always) say that an LED bulb has the same brightness as a traditional bulb.

How to Convert Lumen to Watts

How to Convert Lumen to Watts

Lumens and luminous effectiveness can be used to determine watts. You can’t convert lumens to watts since the two units represent distinct quantities.

The luminous efficacy of energy-saving lamps is great (more lumens per watt).

The luminous flux V in lumens (lm), divided by the luminous efficacy in lumens per watt (lm/W), equals the power P in watts (W). The lumens to watts conversion formula is as follows:

P(W) = ΦV(lm) / η(lm/W)


watts = lumens / (lumens per watt)


W = lm / (lm/W)


What is the power consumption of a lamp that has a luminous flux of 600 lumens and luminous efficacy of 10 lumens per watt (lm/W)?

P = 600 lm / 10 lm/W = 60 W

Read more: LED Power Supply Guide How to choose the best?

Luminous efficacy table

Light type Typical luminous efficacy (lumens/watt)
Tungsten incandescent light bulb 12.5 – 17.5 lm/W
Halogen lamp 16 – 24 lm/W
Fluorescent lamp 45 – 75 lm/W
LED lamp 80 – 100 lm/W
Metal halide lamp 75 – 100 lm/W
High-pressure sodium vapor lamp 85 – 150 lm/W
Low-pressure sodium vapor lamp 100 – 200 lm/W
Mercury vapor lamp 35 – 65 lm/W

***The luminous efficacy of energy-saving lamps is great (more lumens per watt).

Lumens to watts table

If you still can not convert lumens to watts, you can refer our lumens to the watts table below: 

Lumens Incandescent light bulb (watts) Fluorescent / LED 


375 lm 25 W 6.23 W
600 lm 40 W 10 W
900 lm 60 W 15 W
1125 lm 75 W 18.75 W
1500 lm 100 W 25 W
2250 lm 150 W 37.5 W
3000 lm 200 W 50 W

We can see from the chart that replacing a 40W incandescent light bulb with a compact fluorescent (CFL) will most likely require a 10W CFL.

Similarly, if you replace a 75 W incandescent light bulb with a contemporary LED, the LED will most likely use 18.75 Watts.

In each scenario, getting a similar Lumens rating is the most crucial thing to consider when picking a replacement. To replace a 40W incandescent with a CFL, seek one that produces around 600 Lumens. 

***Because LED technology is continually evolving, the wattages we’ve displayed may become obsolete in the future. Simply match the lumen output and you’ll always obtain the desired brightness.

Read more: Power Consumption Calculator Of Any Electrical Equipment

Lumens to watts calculator 

Calculator for converting luminous flux in lumens (lm) to electric power in watts (W).

To get the power in watts, enter the luminous flux in lumens and the luminous effectiveness in lumens per watt, then hit the Calculate button:

Frequently Asked Questions

#1. What is the wattage of a lumen?

Lumens per watt (lm/W) is a luminous efficacy and energy efficiency metric that measures how much visible light is generated for a given amount of electricity. A 60W incandescent light bulb, for example, might generate roughly 900 lumens, resulting in luminous effectiveness of 900/60 = 15 lm/W.

#2. What is the lumen output of a 1-watt LED bulb?

What is the brightness of a 1-watt LED bulb? The lumen output of a 1-watt LED bulb is 90. A 1-watt LED bulb uses the same amount of energy as a 9-watt incandescent light bulb.

#3. How bright are 1000 Lumens in Watts?

Utilitech 1000-lumen LED
Utilitech 1000-lumen LED

A 1000-lumen LED is about the same as a 75-watt incandescent light bulb or a 12-watt LED strip.

#4. How many lumens do you need?

A basic rule of thumb is that a sitting room or bedroom will require around 10-20 lumens per square foot, but a bathroom or kitchen will require around 70-80 lumens per square foot. Simply multiply the square footage of the room by this figure to calculate the lumens required.

#5: What is the formula for calculating lumens?

A lumen is a unit of light measurement. You’ll need to multiply your room square footage by your room foot-candle requirement to figure out how many lumens you’ll need. A 100-square-foot living room, for example, will require 1,000-2,000 lumens from 10-20 foot candles.


Thank you for reading our article, hope the lumen watt conversion guide can help you know how to convert Lumen to Watts! And if you cannot, you can use our Lumens to watts calculator to convert by easy way.

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