What the measurement units lux and lumen are and how they can help you light your home

In order to select the best option for your lighting, it is essential to assess the quality of light intensity. Both concepts are very necessary for a good understanding of the characteristics that will help us reach the best decision. Because the intensity of light required for the kitchen or in a reading corner is not the same as the quality that our office light must provide compared with our bedroom light.

What is a lumen?

But how is the luminous flux of a light source measured? With the measurement known as a lumen. The lumen is part of the International System of Units and is represented by the letters lm. It is established from two different variables: the candela (represented by the letters cd) which measures luminous intensity, multiplied by the steradian (represented by the letters rd), which represents a solid angle unit. In simpler terms, we could say that to determine the lumen, the intensity is multiplied by the solid angle that it covers. Therefore, the lumen represents the unit of measurement for the luminous power emitted by a light source, thus expressing the power of a specific light.

Under European Union (EU) requirements the power in lumens must always be indicated, along with the power consumption in watts. This enables us to determine the efficiency of the bulb, since the ideal is to use the least number of watts to generate the most lumens.

Minimum electrical power consumption

What is lux?

From the lumen (lm) it is possible to determine the lux, which is simply the unit of measurement used to establish the level of illumination. This is much simpler: once we know the lumen of a light, we divide the result per square metre.

This operation is done to determine how much light is being covered within a room; if we fall short, there is a risk that only a certain part of the room will be illuminated. This is why there are general recommendations adapted for each type of surface:

Recomendaciones de lux por estancia

Worktop area (kitchen): 500-600 lux

General space (kitchen): 200-300 lux

Reading/work area (living room, office or bedroom): 500 lux

General space (living room, office or bedroom): 100-200 lux

General space (living room): 200-300 lux

Mirror/dresser (bathroom): 300-500 lux

General space (bathroom): 200 lux

Passage area: 100-200 lux

Current employment legislation stipulates a minimum lux level for a professional working environment to safeguard our health. A light meter is the device used by professionals to measure illuminance and determine whether our workplace meets the legal requirement. Accordingly, it is important to follow the instructions provided by the company to adapt our remote working space.

What is the difference between lumen and lux?

Lumen helps us to understand how luminous flux works depending on the angle at which light is projected. If the angle is very close, the flux will largely be concentrated in a small space. This is the case with table lamps, which direct all their power onto a specific place. Conversely, if the angle is very open, the power of the flux is dispersed.

Lux takes into account the light on the surface to be illuminated: a specific light flux on one square metre is not the same as one distributed over ten square metres.

And although these two units of measurement are related, since the lux is simply the lumen divided by the square metre, they are different and measure two distinct aspects that are equally important.

LED bulbs and their efficiency in lumen and lux

As the table above shows, LED lights are the most efficient in terms of power consumption (W) and light flux power (lm). Their design allows the light they emit to be propagated in the form of a beam with a specific angle, causing the power to be concentrated in this beam and illuminating the largest possible area.

This does not happen with regular bulbs, which emit light evenly around the bulb, without a specific direction. Therefore, a great deal of the light from a conventional bulb is dispersed and lost, reducing the efficiency of this point of light.

Therefore, the ability to direct the light of LED bulbs means their flux (lm) can be concentrated without dispersing over a specific area (m²). This means they are much more efficient and help reduce the cost of your bill.