What is illumination and lux unit ?

Illuminance, measured in lux (lx), is a measure of the amount of light (luminous flux) falling on a surface per unit area. It is a key concept in lighting design and photometry, as it helps us understand how well an area is lit or how much light is available at a particular point. Here's a more detailed explanation of illuminance and the lux unit.

Illuminance (Lux):
• Definition: Illuminance is the luminous flux (in lumens) incident on a unit area (in square meters) of a surface. In simpler terms, it measures how brightly or intensely an area is lit up.
• Symbol: Illuminance is typically represented by the symbol "E" and it is measured in lux (lx).
• Mathematical Formula: The formula for illuminance is E = F/A,
E is the illuminance in lux (lx).
F is the luminous flux in lumens (lm).
A is the area in square meters (m2).

Illuminance follows the inverse square law, which means that as you move farther away from a light source, the illuminance decreases inversely proportional to the square of the distance. The formula for this relationship is as follows.
E =I/d2
I is luminous flux
d is the distance from the source.

Illumination calculator for lux calculation

The following Illumination calculator takes inputs such as lumens per lamp, coefficient of utilization, light loss factor, area per lamp and produces output as Illumination in lux. The lux formula used for the calculation is mentioned below.

Number of lamps (input1) :

Lumens per lamp, in lumen (input2) :

Coefficient of utilization (input3) :

Light Loss Factor (input4) :

Area per lamp, in m2 (input5) :

Illumination in Lux (Output):

Illumination calculation example :
INPUTS : N = 10, Ll = 10600 lumens, Cu = 0.6, Llf = 0.8, Al = 50 meter2
OUTPUTS: Illumination (I) = 1017.6 Lux

Illumination formula

The following Illumination formula is used for Lux calculation. The calculator takes inputs such as lumens per lamp, coefficient of utilization, light loss factor, area per lamp and produces output Illumination in lux.

Illumination Calculation Formula or equation

The formula for calculating illumination (lux) is above which is I = (N * Ll * Cu * Llf)/ A
I = illumination in lux (lx).
N = Number of lamps or light sources.
Ll = Luminous flux of a single lamp in lumens (lm).
Cu = Coefficient of utilization, which accounts for the efficiency of the lighting system. It's a unitless value between 0 and 1.
Llf = Light loss factor, which considers the reduction in light output due to factors such as aging of lamps and dirty fixtures. It's also a unitless value between 0 and 1.
Al = Area in square meters (m2) over which you want to calculate the illumination.

Conclusion : In summary, illuminance (lux) is a fundamental metric in lighting design and photometry that quantifies how much visible light falls on a surface. It helps ensure that spaces are appropriately lit for their intended use, taking into account factors like the luminous flux of light sources and the size of the area being illuminated.

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