Lux Calculation Formula and Illuminance Calculator Guide

Lighting plays a crucial role in creating functional and comfortable spaces. Understanding lux levels and measuring light intensity will help in the design of efficient lighting systems for various environments.

This guide delves into the lux calculation formula and how to use an illuminance calculator for precise lighting measurements. Whether you’re an engineer, architect, or DIY enthusiast, mastering these concepts ensures optimal lighting solutions for your needs.

What is Illumination and the 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’s 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’s measured in lux (lx).

• Mathematical Formula: The formula for illuminance is:

  E = F / A

  Where:

  • 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 / d<sup>2</sup>

Where:

• I is luminous flux
• d is the distance from the source.

Illuminance Calculator

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

Illumination Calculation Example:

• INPUTS:

  • N = 10
  • Ll = 10600 lumens
  • Cu = 0.6
  • Llf = 0.8
  • Al = 50 meter²

• OUTPUTS:

  • Illumination (I) = 1017.6 Lux

Lux Formula

The following 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.

The formula for calculating illumination (lux) is above, which is:

I = (N * Ll * Cu * Llf) / A

Where:

• 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.

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.

Conclusion

Accurate lighting design begins with a clear understanding of lux calculations and illuminance measurement tools. With the lux calculation formula and a reliable illuminance calculator, achieving the right lighting levels for any environment is straightforward. Apply these techniques to enhance visibility, energy efficiency, and ambiance in your projects.