How to calculate the illumination of a room?

What is the correct illumination of a room? For everyone, this concept is different, as someone loves twilight, while someone prefers bright lighting. But lighting technicians will be able to calculate the correct and most effective lighting for each room, taking into account energy savings. Calculate the amount of light - this is to perform a set of works on the selection and placement of lamps in the room, as well as calculate the energy consumption. In this article we will tell readers Elecroexperthow to calculate the illumination of a room by providing the most popular methods and formulas.

Lighting calculation methods

Coefficient method

Illumination plays an important role in people's lives. Calculating it is very simple using the coefficient method. First of all necessary count the number of fixtures (N).

Coefficient method formula

100 * S * E * Kr - the definition of glare, where:

  • S is the area of ​​the room;
  • E - light level of the horizontal plane (indicated in lux);
  • Kr– safety factor (for the house it is 1.2).

U * n * Fl- calculation of the brightness of the lamps, where:

  • U is the coefficient of light consumption by the device (depending on the number of lamps);
  • n is the number of lamps in the device;
  • Fl– luminous flux of one lamp (measured in lumens).

For example: At the workplace (such as an office or kitchen), 3 lights are used. We substitute the data in the formula: 3 = E (cabinet) * 100 * 1.2 (standard illumination). It remains to make a calculation of the brightness of the lamps. And for this it is necessary to know the coefficient of light consumption (U).

In order to calculate it, you need to have a room index, while taking into account the material of the walls and ceiling (reflective). For this:

Light consumption


  • h1 is the height at which the lamps are located;
  • h2 is the height of the working surface;
  • a and b - the length of the walls, the area of ​​the room is known.

After calculating the value, for a complete calculation, it is necessary to find out the remaining data. In the directory you need to look at the reflectivity indices of the materials of the ceiling and walls. The coefficient of light consumption will be lower if the walls are light. Substituting all the data into the formula, you can calculate the illumination of the apartment or premises. Based on the example, then for a room with three lamps you need the following result:

Settlement part

According to the results, it was decided that the illumination of the room should consist of 12 separate lamps that are built into the ceiling. Three fixtures were abandoned.

All reference materials are available on the Internet, as well as below the article, so there is nothing complicated in the calculation. There are many similar calculations in order to calculate the illumination.

Power density

This technique uses data from directories, so it is considered simple. The disadvantage of this method is a large margin in the calculation, which makes it difficult to calculate the cost of electricity and save it.If you look at the fact, then this is a method of estimating the cost of electrical energy. If there is a specific power of light, then it is enough to multiply the number of lamps by the power and divide by the area. The resulting number can be used to establish the approximate power and number of lamps.

Point method

This calculation makes it possible to distribute the lamps according to the area of ​​the room. And this means that using this method you can find out the lighting at a certain point in the room. To begin the calculation by this method, it is necessary to develop a floor plan, determine the design point and place the fixtures.

Point method

This method is complex, therefore it is used in the case when the complex surface of the walls or ceiling or for design decisions. When viewed from the side of saving electricity, this method is considered the most economical.

There are also programs for calculating room lighting. We recommend checking the result using special software!

Prototype application

For this method, the table from the directory is used, where the exact miscalculations of standard rooms are registered. Such miscalculations were carried out more than once, so the data that are listed in the table is correct. There are more unusual methods and formulas for determining the level of light, but they are expensive and are used only for rooms of complex design and layout, or street lighting. For a residential apartment, it makes no sense to apply them.

What is important to know?

Calculating lighting or lighting is a necessary procedure. The calculation is based on two points:

  1. Consideration of all necessary requirements and standards.
  2. Compliance with electrical and construction standards.

For ordinary residents, these standards are not so important, but they must be observed. For example: a staircase in a private house. If you make a calculation, it will be seen that it needs lighting in the workplace. But in practice there are various situations when five fixtures with LED lamps are enough. At the same time, there were still 6 unused cables left in the wall, which were laid there on the basis of a miscalculation. Therefore, do not rush to spend extra money and do covert wiring.

Or another example. The owners decided to make a children's room out of the living room. Lighting in this case should be in the area of ​​the floor. But there was no possibility of directing the light flux in the direction of the floor, so I had to use local lamps, which is not very convenient.

Therefore, it is important to calculate the light when designing the electrical network of a house. If during construction it is necessary to change something, it is best to make a new calculation.

Reference materials

The tables below show the data of U (light consumption coefficient), which are written in the first formula. This is the illumination of the horizontal plane:

Room Lighting Standards

Reflection coefficient

We also recommend watching a useful video on the topic:

Now you know how to calculate the illumination of the room yourself. We hope the formulas and methods provided were useful to you!

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