Lumen to Lux to Candela calculator

It’s not exactly a news item, but we thought this lumen calculator could be a useful addition to your toolkit. It converts between lumens, lux and candelas easily, helping you to identify the lighting solution that best meets the specific requirements of an installation.

With this calculator, you can convert a lumens value of a product into a lux value if you know the beam angle and measurement distance. Enter the distance and angle of the beam (change ‘360’ to your own figure), then enter a value for one of lumens, lux or candelas. The conversions will then be made automatically:

Lumen Calculator
(Lumen to Lux to Candela)

What are lumens, lux, and candelas?

These three words describe the most commonly used units for measuring lighting. They are all related, but represent entirely different things.

  • Lumens are a unit of luminous flux, or more simply the total amount of light emitted by a source in all directions. The lumen measurement (lm) gives the total luminous flux of a light source by multiplying the intensity (in candelas) by the angular span over which the light is emitted – the ‘radiation angle’ in the calculator.
  • Lux is a measure of the illumination of the surface, or how much light is received by a surface. One lux is equal to one lumen per square metre (lux = lumens/m2).
  • Candelas are the SI units of luminous intensity and represent the amount of light emitted from a source in a particular direction. It tells you how bright the light source is – how far away from an object you can be and while still being able to see it.  The unit is the steradian lumen, better known as candela (cd).

As light moves further from the emitter, the more it will be scattered. So the amount of lux in an area or on a surface can vary depending on the distance travelled by the light and the angle with which it is dispersed.
Assuming the same light source, light that travels across less distance and/or is more narrowly focused will appear brighter because the luxes are concentrated in a smaller area than light that has travelled a greater distance and has been scattered over a larger area.

Since both candelas and lumens are units of emitted light, knowing one of the values means you can easily convert to the other.


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