What are Lumens?

The meaning of Lumens as a lighting measurement is the now the only way to accurately tell how bright your lighting fixture will be. This guide tells you exactly what you need to know to compare and choose your lighting fixtures and bulbs with confidence.

Squirrel cage lamp

It’s important to know the lumens of the light bulb or fixture you are buying. Lumens measure how much visible light a lamp produces. Some people will even refer to Lumens as “brightness” in this sense, because it measures that too.

The Meaning of Lumens

Lumens means light output.

Lumen definition is: “a unit of luminous flux in the International System of Units (SI), that is equal to the amount of light given out through a solid angle by a source of one candela intensity radiating equally in all directions.”

Luminous Flux is how much visible light is emitted by a light source or received by a surface.

This unit of Flux is the LUMEN. .

How is Light Measured?

Light and how it effects our environment is quantified most accurately in 4 ways.

Even designers get confused with all this so for quick reference when buying and choosing lighting we need a simple unit of measurement to know how bright it will be and how effectively it will light up your home. This is the Lumen.

Why Are Lumens Important?

As Lumens are a measure of the total amount of visible light emitted by a light source, the higher the Lumens, or brightness, then more visible light is produced by your LED lights and they will be brighter. This is why Lumens are an essential part of understanding how well your light choices will work for you.

How Many Lumens Do I Need?

The more Lumens the brighter your LED lights will be and vice versa. As a rule of thumb, you need one Lumen per square foot of space that needs to have light on it for general lighting purposes in most homes.

In a dining room, you want more Lumens to light up the whole area completely and bright enough for people to see what they are eating at their dinner table. In this case you would need more Lumens per square foot of space in your home because it’s a small concentrated area that needs lighting.

Lumens vs Watts

So what is the difference between Lumens and Watts?

The Watts or Wattage of a light bulb or fixture is the measurement of energy consumed to create light and over the years has become synonymous to brightness, but has never been a unit of how much light is created.

Traditionally, the amount of visible light created from the power consumed to do so was relatively the same across the various types of light available. Therefore how much energy being used became the defining factor of how bright is was. It was never as completely accurate because fluorescent and halogen lamps were more efficient, but when LED arrived as a seriously efficient light source, power consumption could no longer be a comparative unit of measurement.

How Do Lumens Compare to Watts?

As a lumen is the unit of luminous flux, a measure of the total quantity of visible light emitted by a source per unit of time, there is no comparison at all.

So it’s important to note that Watts only measures energy used and not how much visible light created by a bulb or lamp.

For example: 800 Lumens can be created by a 60 watt incandescent bulb or 12W of LED.

Brightness in LUMENS220+400+700+900+1300+
Lumen to watt comparison chart for LED, CFL, Halogen & Incandescent lamps

What Are Lumens in LED Lights?

Lumens in LED lights are an accurate measurement of brightness and as it’s a unit of measurement for visible light it means you can compare them to other Lumen outputs from other sources accurately.

Now that we know how Lumens work, it’s important to make sure when choosing your next LED lamp or bulb that you choose one with a good Lumen value.

What is Lumens Per Watt (lm/W)

The total light output in Lumens divided by the power usage in Watts is a good technique to evaluate lighting products’ effectiveness.

The lm/W is a metric that compares the amount of light emitted by one watt to the quantity consumed by one watt, thus allowing you to compare bulbs based on their efficiency. In other words, it compares how much light a particular wattage puts out against how much heat it creates. As with any type of illumination, more watts equal more Lumens, but Lumens are inversely proportional to watts.

The higher the lm/W value is for a particular lamp, the more efficient it will be at creating light while requiring less power. This can save you money on your electric bill and reduce how much energy you use overall.

Check Lumen Per Watt When Choosing Lumens

It’s important to check Lumen Per Watt when choosing Lumens. This is an ideal way of determining how efficient a lamp can be, allowing you to get the most out of your lighting choices without sacrificing both quality and budget by paying for more than what you need.

The Lighting Facts Label will have this information on there so you can easily check Lumens Per Watt.

The Lighting Facts Label will have all the information you need regarding Lumens and how bright your light is.

Lumens on the Lighting Facts Label

The Lighting Facts Label has to be on every lamp and bulb by law from 2018 in the US. The Lighting Facts Label is very important for Lumens.

When you are choosing your Lumen requirements it is extremely important to look at the Lighting Facts Label on any lamp or bulb that you choose. This will give you all the information necessary for Lumens and how bright they actually are in comparison with other products of their kind.

What are Useful Lumens?

The useful lumens rating was introduced by the EU in order to standardise Lumen ratings.

‘Useful lumens’ is the definition of the amount of light that will fall within a narrowed area, standardised within a 90 degree cone of light that starts at a single point and broadens the further it travels from the source.

The measurement of ‘useful lumens’ is important as it helps you understand how much of the total lumen output created will travel in the direction of 90 degrees from the source, ie how much of it will reach where you may want it to get to.

For example, an A lamp or GLS lamp are non directional and can have a 330 degree spread of light. The stated lumen output of the source is spread throughout that area, some being lost maybe within the lighting fixture it’s in or bouncing back into the room from inside the fixture with some losses of light by the time it reaches the surface below.

This is all to be considered compared to a directional bulb like a PAR GU10 LED which sends the light forwards assisted by a surrounding reflector, so more of the stated lumen output will be included as ‘useful’.

It is worth stating that the lumen output that is not included within the useful range, is still important. Not all light should be directed within a tight cone such as bulbs within shades that need to send light everywhere to ensure a more uniform illumination of the fabric.

Andrew Orange , the owner of Orange Lighting qualified and worked as an interior designer in 1993 before specialising in lighting working on high profile projects based in London. Since starting Orange Lighting Ltd in 2003 he has been sharing his knowledge and unique teaching style mostly to his designer clients, offering practical real life advice born from running a busy consultancy and lighting supply business. Launching in 2020, his blog has evolved into Quick & Easy Lighting, curating some 25 years design experience into making the lighting choice and design process achievable and easy to understand for all.