Updated: January 05, 2017
Anyone who has ever been shopping for a flashlight may have noticed that there are numbers on the box that describe either “lumens” or “candlepower.”
For those who don’t understand what these numbers refer to, it may be a bit confusing trying to decide which flashlight is the best for whatever purpose they have in mind. So, what are lumens and candlepower?
A simple definition of these words is all that is needed to clear up the confusion and to make any flashlight purchase that much simpler.
Candlepower measures the intensity of the beam produced by the light source, though the term “candlepower” is no longer used. Light manufacturers prefer the term “candela,” but the meaning remains the same.
It is called “candlepower” because this measurement was originally based on the light of an actual candle, one with specific structure and dimensions. A light with 10,000 candlepower means it is the same amount of light as 10,000 candles.
It’s important to remember that candlepower/candela is a measure of intensity and doesn’t take into account distance (that’s lumens). Candela only measures how much light is produced at the source of the light. If you were to measure the light coming out of a flashlight right on the lens of the flashlight itself, then you could measure the intensity of the light coming out of that one spot. So when manufacturers label a flashlight’s peak beam intensity as, for example, 12,000 candela, like in this Streamlight TLR-1 flashlight, they are saying that in the most concentrated spot, the intensity of light that is emitted is equal to 12,000 candles.
Lumens refers to the amount of visible light that is created by any type of light source. Just think of it like this: whereas candlepower measures the light given off by a single candle, lumens measure the area illuminated by the candle. Because candlepower and lumens measure different qualities, they have different ratios, with 1 candlepower = 12.57 lumens.
If it’s difficult to envision the amount of light measured in lumens, it also might help to think about how household lightbulbs are measured in watts. Watts are another measurement of light, but they are not a good indication of how much light is put out by the source—watts measure how much energy is used by the bulb. It’s not an efficient way to measure light output, but still, most people can envision how much light is emitted by a lightbulb of however many watts. A 25 watt lightbulb, for instance, will provide a fairly low amount of light. You could use a 25 watt lightbulb for a nightstand lamp. That 25 watt light bulb is equal to about 230-270 lumens. The Lumen Output illustration provides a visual example of the watt to lumens ratio:
Lumens are a more efficient way of measuring light output because they also take distance into account. A lumen measures how much light reaches the object that needs to be lit. As an example, if you have a one foot tall candle and you place an object one foot away from the candle, the lumen measures how much light is able to reach that object from a one-foot tall candle at a distance of one foot. As you’re shopping around for flashlights, you’ll notice that most flashlights are measured using lumens. The reason for this is pretty simple. Flashlights are typically used to illuminate objects at a distance. So a user needs to know how much light is going to shine on that object. The best way to measure that is to use lumens.
When trying to measure how many lumens equals a certain amount of candlepower, just remember that 12.57 lumens is the equivalent of 1 candlepower.
If you want to figure out the amount of lumens in a light source only measured in candela, simply grab a calculator and multiply the candela count by 12.57, and you will have the lumen count.
Convert Candela to Lumens
Convert Lumens to Candela
When doing a comparison of candlepower versus lumens, the best thing to do is to decide what the flashlight will be used for. If an intense beam is needed, such as if you were to need a light that could pierce the murky depths of a swamp, then the candela rating would be the more effective spec to look out for, since it will tell you how intense of a light that flashlight is capable of emitting.
If, however, you need the flashlight to illuminate a rather large area, it is best to choose a light with a higher lumen count.
Why Do the Candela and Lumens Measurements Not Match Up?
So you might have noticed in the flashlight that was used as an example earlier that there was a mismatch between the candela and the lumens. The flashlight says it is capable of a 12,000-candela peak beam intensity but it also claims to have an 800 lumens max output. Our conversion calculator shows that those two do not equate!
Actually both ratings are possible. The reason for this is that flashlights nowadays are often engineered with complex lens designs. In the flashlight we’ve been talking about, Streamlight boasts it has a TIR optic that produces a concentrated beam with optimum peripheral illumination. This is a sophisticated way of saying they have engineered the lens to have angles that both concentrates the light in order to increase the candela intensity and allows enough of that light to be projected outwards to maximize the lumens output.
Using Lumens to Determine the Flashlight for Your Needs
When you are choosing a flashlight, of course, you are probably not going to want to use a calculator to determine how much candlepower would be equivalent to the lumens rating on your flashlight. And as the Streamlight flashlight shows, there are ways to manipulate the candela intensity and lumens output of a flashlight, so the conversion calculator won’t be the only thing you need to choose the flashlight that is right for you. Since most flashlights are measured in lumens though, and since flashlights most often are used to illuminate objects at a distance, I have provided a series of reviews of flashlights, organized by lumens categories (300, 500, 1200, 4000, and 5000). I also try to describe the types of flashlights that utilize these various lumens (e.g. pocket flashlights, tactical flashlights, spotlights, etc), so you can get a better sense of the kind of flashlight you are about to invest in.