Candela formula and lux formula

Lux and candela are units of measurement used in the field of photometry to quantify the intensity and brightness of light. Lux measures the illumination or brightness of a surface, while candela measures the luminous intensity of a light source. let us look at their formulas and calculations.

Candela (cd): Candela is the base unit of luminous intensity. It measures the amount of light emitted in a specific direction by a light source.

Lux (lx): Lux is a unit of illuminance, which measures the amount of visible light that falls on a given surface area. It indicates how bright the light appears to the human eye on a particular surface.

Candela formula is as follows.
➨Candela (Cd) = Luminous Flux (lm)/Solid angle (Steradians)
Luminous Flux (lm) is the total amount of visible light emitted by the source.
Solid angle is a measure of the spread of light in 3-Dimensional space as viewed from the source. For a complete sphere, it is 4π steradians.
Candela calculation example : Assume that a light bulb is emitting 800 lumens of visible light uniformly in all directions. Calculate luminous intensity of this light source in units of candela.
Candela = 800 lm/4 *3.14 = 63.66 cd

Lux formula is as follows.
➨Lux (lx) = Luminous flux (lm)/Surface area (m2)
Surface area (m2) is the area on which light is falling
Lux calculation example : Assume that there is a desk with an area of 2meter2 and 800 lumen light bulb is placed directly above the desk. Calculate illuminance (in units of lux) on the desk.
Candela = 800 lm/2 m2 = 400 lx

Lux to candela calculator


Illuminance (Lux) as input :

Distance from light source in meters :


Luminous Intensity in Candela :

EXAMPLE of lux to candela conversion :
INPUTS: Illuminance (in Lux) = 100 , Distance from light source = 10 meters
OUTPUT: Luminous Intensity in candela = 10000

Candela to lux converter


Luminous Intensity in candela :

Distance from light source in meters :


Illuminance (Lux) as output :

EXAMPLE of Candela to Lux converter :
INPUTS: Luminous Intensity in candela = 10000 , Distance from light source = 10 meters
OUTPUT: Illuminance (in Lux) = 100

Lux to candela conversion formula

Following equation or formula is used for Lux to Candela conversion and vice versa.

lux to candela conversion formula

Conclusion : In summary, candela measures the intensity of a light source, while lux measures the brightness or illuminance on a surface. The calculations involve luminous flux, solid angle, and surface area, depending on whether you are dealing with candela or lux.

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