# Lumens to candela calculator

Convert luminous flux from lumens (lm) to luminous intensity in candelas (cd) effortlessly. Ideal for lighting design, beam angle calculations, and LED specifications. Accurately convert lumens to candela using this convenient online tool.

## what is Lumens to candela

Converting lumens (lm) to candela (cd) requires additional information about the beam angle or solid angle over which the light is distributed. Luminous intensity, measured in candelas, indicates the concentration of light within a specific solid angle.

To convert lumens to candela, you need to know the solid angle in steradians (sr) over which the luminous flux is distributed. The formula for this conversion is:

Luminous Intensity (cd) = Luminous Flux (lm) / Solid Angle (sr)

Without the solid angle information, it is not possible to provide an accurate conversion from lumens to candela.

When converting between these units, it is important to consider the angular distribution of light from the source and the specific application requirements. Proper measurement and specification of luminous intensity require knowledge of the beam angle or solid angle over which the light is emitted.

## Lumens to candela calculation

For uniform, isotropic light source, the luminous intensity *I*_{v} in candela (cd) is equal
to the luminous flux Φ_{v }in lumens (lm),

divided by the solid angle *Ω* in steradians (sr):

*I*_{v(cd)} = *Φ*_{v(lm)} / *Ω*_{(sr)}

The solid angle *Ω* in steradians (sr) is equal to 2 times pi times 1 minus cosine of half the
cone apex angle *θ* in degrees (º):

*Ω*_{(sr)} = 2π(1 - cos(*θ*/2))

The luminous intensity *I*_{v} in candela (cd) is equal to the luminous flux Φ_{v }in lumens (lm),

divided by 2 times pi times 1 minus cosine of half the apex angle *θ* in degrees (º):

*I*_{v(cd)} = *Φ*_{v(lm)} / ( 2π(1 - cos(*θ*/2)) )

So

candela = lumens / ( 2π(1 - cos(degrees/2)) )

Or

cd = lm / ( 2π(1 - cos(º/2)) )

### Lumens to candela Example#1

Find the luminous intensity *I*_{v} in candela (cd) when the luminous flux Φ_{v }
in lumens (lm) is 337lm and the apex angle is 60°:

*I*_{v(cd)} = 337 lm / ( 2π(1 - cos(60°/2)) ) = 400.3 cd

### Lumens to candela Example#2

Assuming you have a light source with different luminous flux values in Lumens (lm) and you want to convert them to Candela (cd), you can use the following table:

Luminous Flux (lm) | Solid Angle (sr) | Luminous Intensity (cd) |
---|---|---|

1000 | 4π | 79.577 |

500 | 4π | 39.789 |

200 | 4π | 15.915 |

100 | 4π | 7.958 |

To convert the luminous flux to luminous intensity, you need to divide the luminous flux by the solid angle for each value.

For example, if the luminous flux is 1000 lm and the solid angle is 4π sr, the luminous intensity would be 1000 lm / (4π sr) = 79.577 cd.

Similarly, for a luminous flux of 500 lm and a solid angle of 4π sr, the luminous intensity would be 500 lm / (4π sr) = 39.789 cd.

You can follow the same calculation for other values in the table.

Please note that this conversion assumes a uniform distribution of light and equal brightness in all directions. In practice, the actual luminous intensity may vary depending on the specific characteristics of the light source.