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Convert Candlepower to Lumens & Back… Why and When?

First off lets just say that they are different things and different ways to measure light. But, this question is still asked all of the time so before we get to complex in the difference here is the quick answer.

To get from Candlepower to Lumens we are going to multiply Candlepower by 12.57 to get Lumens.

To get from Lumens to Candlepower we are going to divide Lumens by 12.57 to get Candlepower.

If you want to see what the current highest lumen flashlights are check out our article on the most powerful torches available.

Now lets get a little more specific since this is not the whole story and we need to modify what we are talking about here.

What is Candlepower?

The term Candlepower is an old time way that light used to be measured and it speaks to how much light would come off of 1 candle and hit a specific target. It was used to calibrate and measure light outputs. One light that was the control would be compared to another by finding the distances that they would need to be from a target so the targets looked like they were illuminated the same amount.

These days Candlepower is used as a synonym for the scientific measurement of Candela. Candela measures the amount of light in a particular direction.

Candlepower is a great name for one of the top flashlight forums.

What is Lumens?

Lumens comes from Luminous Flux and is the total amount of light that comes out of a source of light.

Candlepower vs Lumens Comparison What Is The Difference?

The big difference here is that Candlepower and Candela measure light is a direction while Lumens measure all light is all directions.

So how do we have a way to convert these numbers if they are not measuring the same thing?

We what we do is figure out a way to get our Candela measurement in all directions.

So to imagine this we assume that our light source is in ball (sphere) and then the inner surface area of that ball is all of the directions of the ball.

Mathematically we find surface area by the formula Surface Area = 4π x radius.

Now with a little jumping in order to make the image work we will say that the inner surface area represents all of the light which is Lumens and the radius line represents the Candela in a specific direction.

So we are left with a formula of Lumens = 4π x Candela.

Now for the last step in our conversion formula. What is 4π? We learned to memorize π = 3.14 so…

4 x 3.14 = 12.56

That is really close to that 12.57 that me mentioned in the beginning of the article. Actually pi is more than 3.14 and if you do the actual calculation you get 12.56637… and if we want only 2 decimal points we should round up to 12.57.

When Does Converting Make Sense?

Converting Candlepower to Lumens or Candela to Lumens makes sense if the measurement of Candela is given in Spherical Candela and is intended to represent the total light output of the light.

An example of this is when a light bulb or lamps brightness is given in Candela or Candlepower. Obviously this is not supposed to be a representation of light in a single direction. So they are giving us a number for Spherical Candela

In flashlights we often find both Lumens and Candela on the same standardized ANSI FL1 table.

Above we have the ANSI chart for the Imalent MS18. In this case the Lumens represents the total light output and the Candela measurement is measuring the peak beam intensity at a certain distance.

Candela is actually measured in lux and then the distance is accounted for in a formula.

Since we are actually going for the highest measurement of light in a specific direction there is no reason to change these numbers into Lumens.

Flashlight Peak Beam Intensity Into Lumens

We can do this but what the the number represents is if that super bright spot in the beam was the same all of the way around in a full sphere. Which does not really make sense.

But lets give it a go… Using the Chart above we will take peak beam intensity and multiply by 12.57.

458,000cd x 12.57 = 5,757,060 Lumens

Wowzers! That would be a really bright flashlight!

The other way around, Lumens to Candlepower… representing if all of the light was evenly spread around the inside of a sphere how much light would go in a specific direction.

100,000 Lumens / 12.57 = 7,955 Candlepower.

These numbers are way off from what the actual number are.

This is because the purpose of a flashlight is to shoot light in a specific direction and to do that we use reflectors that focus and intensify the spherical light to concentrate the way we want.

With that said there is no way to standardize a way to convert from the Lumens on a ANSI FL1 chart to the Peak Beam Intensity Candela reading. Simply because it relies on many factors like reflector design and number of LEDs that are different in every flashlight.

Color Temperature Throws This Way Off… For Our Eyes

One last thing to consider when looking for flashlights and looking at these numbers is color temperature.

Our eyes and our brains are designed to see different colors with more intensity. So something that is white but more toward the blue or green spectrum will stand out way more than something in the yellow or orange or red spectrum.

Even if the total Lumens output or peak beam intensity is the same.

So when you are considering a flashlight you should think about what it is for. If you just want to see things then brighter and bluer white might be better.

But, if you want to see things and for it to have a similar color to what it would look like if it was in sunlight then you might want to consider a more neutral tint with a better CRI.

Well we hope you learned something in this article. If you want to learn more about flashlights head over to our homepage and poke around.

If you are looking for a specific type of flashlight we recommend going to our best flashlight buyers guide list and from there you will see the list of all of our buyers guides listed out by type.