Skip to content

How to Calculate Lumen and Lux for a Lighting Project


When it comes to lighting a space, it's important to understand two key measurements: lumen and lux. Lumen is a unit of measurement for the amount of light emitted by a source, while lux is a unit of measurement for the amount of light that falls on a surface. By understanding these measurements, you can ensure that a space is properly lit and that the light fixtures you choose will provide the right amount of illumination.

Calculating Lumen: To calculate the total lumen output needed for a space, you will first need to measure the square footage of the area to be lit. Once you have this information, you can use the following formula to determine the total lumen output needed:

Square footage x Lumen per square foot = Total Lumen Output

For example, if you have a room that is 500 square feet and you want to achieve a level of 50 lumen per square foot, the total lumen output needed would be 25,000 (500 x 50).

Calculating Lux: To calculate the level of lux needed for a space, you will first need to determine the distance between the light source and the surface that you want to be illuminated. Once you have this information, you can use the following formula to determine the level of lux needed:

Lumen output / Distance² = Lux

For example, if you have a light source that emits 1,000 lumen and it will be placed 3 meters away from the surface to be illuminated. The calculation will be 1,000 / (3*3) = 111 lux.

It's important to note that the level of lux needed can vary depending on the type of space and the task that will be performed there. For example, a reading nook may require a higher level of lux than a television room. A general rule of thumb is that a living room needs around 50-75 lux, a kitchen or a bathroom needs around 75-100 lux, and a workspace such as an office or a craft room needs around 300-500 lux.

In conclusion, calculating the lumen and lux needed for a lighting project is an important step in ensuring that a space is properly lit. By understanding these measurements and using the formulas provided, you can make sure that the light fixtures you choose will provide the right amount of illumination for the specific task and space.