What Are Lumens?

November 7, 2023

You want to purchase a new light for your home. What would be your primary consideration? Of course, one of the many factors that comes into consideration is the brightness of the light.

You want the light in the study room to be as bright as possible to serve its primary purpose. Similarly, you want the dimest light as night light in your home so that your sleep is not disturbed. For spaces like the living room and bedroom, you want the light to provide enough brightness but not too glaring.

The brightness of a light, whether LED, incandescent, or fluorescent, is called lumen. In fact, it is the visible light from a light source. When you check the cover of a regular light bulb, you will notice the lumen mentioned on it.

What are lumens?

Lumens, written as lm, is an international unit of measurement. It is a scientific unit that refers to the brightness or the amount of light the human eye gets from a bulb. It is the emission of the luminous flux. The higher the lumen, the greater will be the brightness of the bulb.

Till the advent of LED lights, watts were used to indicate the brightness of the light. The presumption was that the higher the Watt, the brighter the light.

But Watt measures the energy used by the bulb and not the light produced by it. Thus, with the increased usage of LED lights, the term lumen began to be widely used. Lumen indicates the brightness of the light produced by a bulb.

What are the benefits of using lumen?

The main advantage of using lumen is that you can easily figure out how many lights to use in a room to get the desired brightness.

If you know the lumen value of light and the square feet of the room, you can easily decide the number of lights required in a room. Thus, budgeting for light becomes easier.

How many lumens do you need?

The amount of lumen you require for a room depends on several factors. You should consider the size of the room, its height, the color scheme of the room, the task you are carrying out in the room, etc., while deciding on the lumen.

Ideally, there are two factors that you should consider while deciding on the lumen.

Square feet of the room:  Square feet are the product of the length and width of the room. If a room is 10 feet wide and 10 feet long, the square feet of the room is 10*10= 100 sqft.

Footcandle: Footcandle means how bright the light will be one foot away from its source. The light requirement varies depending on the room and the task carried out in it.

To determine the lumen required for a room, you should multiply the square feet of the room by the foot-candle.

If the room has dark-colored walls and furniture, you need lights with more lumen to make the room look brighter. On the other hand, if the wall color is white or pastel shades, lights with less lumen are enough.

How many lumens are required for a residential space?

The living room and bedroom are rooms for relaxation where too much brightness is not required. Thus, the lumen per square foot required will be 10-20.

This increases to 20-40 for general kitchen lighting, where slightly brighter light is required. In the kitchen stove and sink area, more brightness is required as most of the tasks are done in these areas. Thus, the lumens per square foot required is 70-80.

In the case of a bathroom, the lumens per square foot of 20-40 is required for lighting the general area. For areas like bathroom sink and vanity where most of the personal grooming takes place, bright lights with a lumen of 70-80 are required.

On the other hand, the hallway or the foyer area requires minimum lighting as not many activities are carried out there. Thus, a lumen of 5-10 is enough in these areas.

For spaces like the garage and storage room, you can go for a lumen of 10-20 unless the space is used for more practical purposes. 

lumens residential space requirement

It is always best to layer the lighting depending on the room and the task carried out. This adds to the functionality and aesthetics of the room. For e.g.; in a bedroom, the general lighting can have a lumen of 10-20. But if there is a reading corner in the bedroom, you can install additional light in that area with a lumen of 40.

How many lumens are required for industrial and commercial spaces?

For lights used for industrial and commercial purposes, the lumen per square foot varies depending on the nature of the work. For potentially dangerous work, lights with more lumen are required, as every aspect of the work should be clear. Similarly, in high-precision areas like labs, the lumen should be high.

In commercial spaces like retail shops, the lumen depends on the type of product being sold. For eg, a jewelry shop requires light with more lumen per square foot than a toy shop.

lumens commercial space requirement

How do you convert watt to lumens?

As mentioned earlier, watts were the preferred means of measuring the brightness of a bulb till sometime back. But that is not the case anymore.

Now, you should check the bulb’s lumen to decide how bright or dim it is.

Below is a table that converts watts to lumens.

convert watt to lumens

Thus, if your room has a 20 W LED bulb and you want to replace it, you should go for a light with 1600 lumens. Similarly, a 40 W incandescent bulb uses 40 W of power and produces 450 lumen light.

However, the lumen measurement can vary slightly depending on the manufacturer and age of the lamp. Similarly, measurement can be changed depending on whether the light is clear or frosted.

What is lumen vs useful lumen?

Lumen, as we have explained earlier, is the brightness of a light source.

But the brightness from a light source, like a bulb, is emitted in all directions. While some amount of light may be useful, some may not be useful. Thus, the EU has introduced a rating called “useful lumen”.

Useful lumen refers to the brightness of the useful light emitted from a light source. The useful lumen will be lower than the total lumen from a light source.


Having lights with the correct brightness can add to the aesthetics and functionality of any space. Thus, you should check the correct lighting requirement of any space before purchasing a light. Similarly, you should also pay attention to the lumen of the lighting fixture so that you get the right brightness.

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