How Many Lights In A Room? How To Calculate The Suitable Number ?

How To Calculate The Suitable Number Of Lights For A Room

LED lights supply sufficient brightness to make the room more presentable and better for our eyes. The only terrain challenging us in getting these benefits is: How many lights in a room for adequate brightness? Have you ever felt that your living room has too little or too much light? Or are you wasting electricity by installing too many light bulbs? 

With this article, Best Led Lights will provide a guide to calculate LUX, lumens, and the number of lights in a home so you can save electricity but still fulfill your demands.

Distinguishing Watt, Lumen, And Lux

Many people mistakenly think that they can compare the brightness of lights by their wattages (Watts). However, Watts is a measure of energy consumption, not brightness. The technical term related to the brightness of a light is luminous flux, known as lumen. The larger the luminous flux values, the brighter the light gets. In short, lumens are the principal measure of the real light output of different lighting devices. 

As a result, the first question that arises when calculating how many lights are in a room is: How many lumens are necessary to light up this room? Once you have the answer, then you can continue to calculate the number of light bulbs, type of lights, correlated color temperature, and wattage. 

In addition, the amount of light output is also measured by LUX. Lumen is the luminous intensity, whereas Lux is the amount of light per square meter, i.e., lumen/m². Almost every LED bulb refers to technical descriptions related to lumens, watts, and LUX.

How To Calculate The Suitable Number Of Lights For A Room

Let’s refer to the formula below to calculate how many lights are needed to light up each room.

(Note: This formula is only approximate since the number of lights also depends on other factors such as type of light, the number of furniture, the furniture layout, and colors, personal preferences, etc.) 

There are two things you should pay attention to when using this formula to calculate.

  • Ground Area:

The area of the room to install the lights is:

S = length x width

  • Recommended Lumens from Lighting Designers

Each space requires different levels of lighting. A gallery demands more light than a library; a family living room needs more light than a bedroom. Below are the recommended light levels by space from lighting experts:

Space Light level

1 LUX (lx) = 1 lumen/m²

Conference room, meeting room 500 lx
Classroom 300 lx
Stairs, corridors of apartment buildings and skyscrapers 750 lx
Bedroom 150 lx
Living room 150 – 300 lx
Family kitchen 400 – 800 lx
Bathroom 400 – 800 lx

We have the following formula to calculate how many lights are needed:

Illuminance = The lamp power (w) x Luminous Flux (lm/w) x The number of lights used  Room area(lumens/m²=LUX)

=> The necessary number of lights = Room area x The standard illuminanceThe lamp power x  Luminous Flux

Example: Calculate the number of LED bulbs needed for a living room with an area of 14m².


  • According to the recommended light levels by space, a family living room should have a minimum illuminance of 150 LUX (i.e., 150 lumens/1m²).
  • The room area is 14m².

Calculate The Total Amount Of Light Lumens For The Whole Room

From the formula LUX=lumen/m², we have the formula for total lumens: Total lumens = The Standard illuminance (LUX) x Room Area (m²) = 150 (LUX) x 14m² = 2100 lumen.

Calculate The Total Power of Lights Needed

A high-quality LED bulb produces approximately 100 lumens per watt. This parameter is provided by the distributor or indicated on the product package.

=> Total power (w) = 2100/10 = 21 W

Calculate The Number Of Lights Needed

The number of lights needed = Total power (w): The power of a single light (W)

Thus, if you pick a 6W LED bulb, the number of lights you’ll need is 21/6=3,5

=> It means that you will need four 6W LED bulbs for a 14m2 living room. Similarly, if you do the same calculation with other lights of different power levels, you will get a relative answer on the number of lights.

Factors Affect The Number Of Lights In Each Room

Aside from calculating the number of lumens to get the right number of lights for each room, these factors below also impact the number of lights and lighting distribution in the house:

  • Color of the walls and interiors: If the house has dark walls and wooden furniture, it requires more lights than the others.
  • Ceiling height: If the ceiling is higher than the average in interior architecture, it would be necessary to install more lights than usual.
  • The number of furniture in the house: If the living room has a lot of furniture with sophisticated and complicated decorative items, it requires more lights than other rooms.
  • Small and large lights: In fact, many low-power luminaires placed at the proper distance in the room give more light efficiency than a single high-powered luminaire.

In fact, there are two ways to bring light into a room. The first option is to add additional light sources (or bulbs), while the second is to utilize brighter bulbs.

Bright lights can induce eye strains, so people tend to use more light sources that are less bright than using a lot of bright bulbs. 

Also, take note of the number of sockets on the fixture and the lumen count on the bulbs you buy. Consider upgrading to a fixture with more sockets or adding track lighting, lights, or sconces if this isn’t enough.


Now that you’ve got the formula to calculate how many lights in a room! Keep in mind that our information above is only standard recommendations. You can install more or fewer LED bulbs than the calculated number, according to your preference.

However, the best approach is to aim high and install dimmers to bring the light level down to acceptable levels.

Above is how to calculate lumens to determine the number of LED bulbs needed for various areas. You can contact Best Led Lights via 0913 703 757 to get a free consultation on lighting plans for your family.