# Online Lumens to lux Calculator

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# Lumens to lux calculator

Luminous flux in lumens (lm) to illuminance in lux (lx) calculator and how to calculate.

Enter the luminous flux in lumens, select area unit type, enter radius in meters for spherical light source or surface area

in square meters for any light source and press the *Calculate* button to get the illuminance in lux:

#### Lumens to lux

When purchasing a lamp, it is nice to know how much light the lamp is giving out exactly. Sometimes this is indicated in Lumen and sometimes in Lux. What do these values mean and what's the difference?

Lumen is the unit of the light current. This indicates the total amount of light emitted by the light source, no matter what direction it is. In Lumen, efficiency is especially important because it indicates how efficient the light source converts power into light. This is called the Lumen / Watts ratio (Lm / W). With LED lights this value is much higher because they need less power to generate a particular Lumen current.

Lux is used to measure the amount of light output in a given area - one lux is equal to one lumen per square meter. It enables us to measure the total "amount" of visible light present and the intensity of the illumination on a surface. Thus, it is important in what direction the light source shines. This value is irrespective of the number of light sources it uses, the colour or the structure where the light shines. If the amount of Lux is indicated by a lamp, it is usually in the centre of the beam where the light intensity is highest.

#### The difference

The difference between lumen and lux is that the lux takes into account the area over which the luminous flux (lumens) is spread. A flux of 1000 lumens, concentrated into an area of one square metre, lights up that square metre with an illuminance of 1000 Lux.

#### For example:

A 500 Lumen light source illuminates 1 square meter with 500 Lux. The same light source that needs to illuminate 10 square meters, which illuminates this area with only 50 Lux.

#### Lumens to lux calculation formula

Calculation with area in square feet -

The illuminance *E*_{v} in lux (lx) is equal to 10.76391 times the luminous flux *Φ*_{V}
in lumens (lm) divided by the surface area *A* in square feet (ft^{2}):

*E*_{v(lx)} = 10.76391 ×* Φ*_{V(lm)} / *A*_{(ft}2_{)}

The illuminance *E*_{v} in lux (lx) is equal to 10.76391 times the luminous flux *Φ*_{V}
in lumens (lm) divided by 4 times pi times the squared sphere radius r in feet (ft):

*E*_{v(lx)} = 10.76391 ×* Φ*_{V(lm)}* *
/* *(4⋅π⋅*r*_{(ft)}^{2})

#### Calculation with area in square meters

The illuminance *E*_{v} in lux (lx) is equal to the luminous flux *Φ*_{V}
in lumens (lm) divided by the surface area *A* in square meters (m^{2}):

*E*_{v(lx)} = *Φ*_{V(lm)}* *
/* A*_{(m}2_{)}

The illuminance *E*_{v} in lux (lx) is equal to the
luminous flux *Φ*_{V}
in lumens (lm) divided by 4 times pi times the squared sphere radius r in meters (m):

*E*_{v(lx)} = *Φ*_{V(lm)}* *
/* *(4⋅π⋅*r *^{2}_{(m}2_{)})