Conversion lumens to watts – Efficiency estimation solution

Conversion lumens to watts

If you’re thinking about calculating lumens per watt, you’re probably shopping for bulbs. An easy way to understand these quantities about a bulb is to consider the number of watts as the energy input to the bulb and the number of lumens as the energy output. Just remember that is an approximation because lumens are actually units of brightness, not energy.

The number of lumens per watt is a characteristic of each bulb and a measure of bulb efficiency. It depends on a number of factors, including how the bulb produces light, the quality of the materials on which the bulb is made, and how much input energy is wasted as heat. The packaging tells you how much electricity each bulb consumes and how much light it emits. The number of lumens per watt is simply the ratio of these two numbers.

In this article, we will share with you how to conversion lumens to watts

What is Lumen?

Get ready for some science and math jargon you may not have heard before. One lum is defined in the SI (metric) system as the amount of luminous flux emitted per second in a unit angle of a steradian equal to a source of a candela. Steradian is simply an area far from r from the source by a circle of area r2.

What is Lumen?
What is Lumen?

The device dates back to a time when candles provided all light and luminance measured with candlesticks, which is still true in today’s lighting industry. If you place a candle one foot away from the wall and draw a square 1 foot on the wall, the amount of light illuminating that square equals one lum.

What is Watt?

One watt is a unit of energy in an SI system. In that system, work and energy are measured in joules, and because power is the speed at which the job is done, one watt equals one joule per second. Power in a circuit, which is equal to the voltage on the circuit multiplied by current, is also measured in watts.

What is Watt?
What is Watt?

The capacity of a bulb is how much energy the bulb consumes, and what electricity bill you will pay in the end. Energy doesn’t produce light, but you can’t convert lumens into watts and back because not all input energy goes into light production. The best thing you can do is to set the ratio of lumens to watts, which is the luminous efficiency of your bulb.

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Compare bulbs with a Watts versus Lumens chart

When you shop for light bulbs, you want to know how much the bulb produces and how much energy it consumes. You will find that information on the package. You can compare bulbs by consulting a watts chart with lumens that you can find online or in any lighting store. When you do this, you might be surprised by the amount of CFLs, LEDs, and even halogen bulbs that consume less energy to give you the same amount of light as an incandescent bulb.

Compare bulbs with a Watts versus Lumens chart
Compare bulbs with a Watts versus Lumens chart

For example, a 100W incandescent bulb produces about 1,600 lumens, giving an efficiency of 1,600 / 100 = 16 lumens per watt. On the other hand, a halogen bulb consumes only 72 watts for the same brightness, making its performance 1,600 / 72 = 22 lumens per watt. A CFL bulb consumes even less energy – just 26W – so its efficiency is 61 lumens per watt. Finally, the LED bulb, most efficient, consumes only 22 watts for an efficiency of 73 lumens per watt.

If you think about equivalent luminescence output, you will only need 22W of power for the LEDs to match the performance of a 100W incandescent bulb. This means LEDs have about five times lower operating costs than incandescent bulbs.

Conversion lumens to watts

1w equals how many lumens

  • In the past, when high-efficiency lighting was introduced, if we bought conventional incandescent or fluorescent lighting equipment, we often paid attention to Watts capacity.
  • Many people believe that the larger the Watts capacity, the higher the amount of light emitted and the brighter the lamp. But in fact, Watts is just a unit of measuring the amount of power consumed and the lamplight depends on lumens.
  • Thus, the higher the lumen index, the brighter the bulb, while Watts is the higher the power index, the more power is consumed.

Lumen = Wattage of Bulb x Luminous Efficacy

Conversion lumens to watts
Conversion lumens to watts

Lumen to watt panel

Lumens Ball




  / 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

Are the parameters on the LEDs in lumens or watts?

– In the past, when buying lighting equipment such as incandescent or fluorescent lamps, we often paid attention to watts of wattage, and by default the larger the wattage, the brighter the lamp. This is only partially true.

In fact, the amount of light emitted from the bulb is measured in lumens, not watts, watts are only a measure of the power consumption of the light source only.

– When high-efficiency luminaires were introduced, buyers began to notice lumen units. Lighting experts also advise that consumers pay attention to this parameter written on the package or supplied from the manufacturer.

– Ordinary incandescent lamps only have an efficiency of about 10-20 lm/watt, fluorescent lamps are about 40-50lm / watt and the highest is LEDs from 80-100 lm/watt. Currently, there are high-end lamps that can reach 150lm / w.

– LEDs are considered to be energy-efficient because they provide large lumens of light (luminous flux) with small power consumption. Example: A 3W led lamp provides 300lm (100lm / w) luminous flux ~ 15w incandescent lamp (20lm / w) ~ 8w fluorescent lamp (40lm / w).

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Frequently asked questions

  • Was Lumen helpful?

For bulbs shaped like circles, spheres, candles, … the total lumen output is calculated for all directions. For this reason, some light sources may not be very useful in lighting but they are still counted in the total luminous flux (lumens).

From there, a concept was introduced with the aim of evaluating “useful lumens”. This is a useful measurement of light emitted in a light source within a 90-degree cone frame. The “useful lumen” rating is often lower than the total output luminous flux and provides a critical rating to the lamp manufacturing process.

LEDs provide luminous flux that is more useful than other lighting technologies because they emit directional light. But so, you can carefully check the Lumen parameters on the solar LED product lines to be able to understand and choose the right product for your needs and circumstances.

  • How many lumens (luminous flux) is required for a room

In fact, to be able to find yourself a certain number of lumens for a room will be very difficult because this will greatly affect each area, room type as well as some other factors such as the height of the ceiling, painted walls, interior decoration, and personal preferences. Each area will need a certain amount of lumens.


  • Kitchen: 300-400 lumens
  • Living room: 400-500 lumens
  • Corridor: 300 lumens
  1. Choose LED by  watts or lumens

Lumens: A measure of light emitted by a light source, whether it’s an LED, fluorescent, halogen, or incandescent light and it is also called luminance. Example: A standard 100-watt incandescent bulb produces about 1,500 – 1,700 lumens.

Watts: Not a measure of brightness; instead, it is a measure of the amount of electricity (or energy) consumed by a light bulb to achieve the required brightness.

Each type of light sources such as LED, fluorescent, halogen, or incandescent has a different lumen/watt ratio. Below we use lumens as a measurement to make sure the led lights have enough light for the space we want.

Choose Led lights according to Lumens


With these details on conversion lumens to watts, we hope they will be of help to you. In addition to the formulas and conversion lumens to watts outlined, you can also convert units easily through available computers on the website.

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