Beam Calculator

Basic Calculation

I know the beam angle and throw:  I know the beam diameter and throw:
Beam Angle (θ) °Beam Diameter (O) m
Throw (T) mThrow (T) m
Beam Diameter (O) mBeam Angle (θ) °

Advanced Calculations

Beam Angle (θ) °  Throw (T) m
Source Distance (D) mFocus Angle (f) °
Source Height (H) mBeam Depth (Y) m
  Beam Width (X) m
Most of the entertainment lighting we deal with are directional spot lights. As a result we need to pay attention to the relationship between beam angle, throw distance and spot diameter.

The beam angle indicates the angle at which the luminous flux passes out of the LED spotlight. The beam angle has a direct influence on how large the produced light cone appears in the room. The mathematical relationship between beam angle, distance and diameter can be found below.

With integrated prisms or diffuser lenses, modern LED spotlights are now available with beam angles from 10° to 120°.

In the light circle, the beam angle defines the area where the lamp radiates at least half (50%) of its maximum luminous intensity. The full luminous intensity (100%) is only achieved exactly in the center of the light circle.

The field angle defines the outer area in the light circle where the lamp radiates up to one tenth (10%) of its maximum luminous intensity. Even outside the field angle it is not completely dark, small parts of the luminous intensity are still emitted here as scattered light.

The beam angle determines how large the generated light circle appears on the illuminated object. An important factor here is also the distance between the light source and the illuminated object. 

There is also a direct correlation between the beam angle and the brightness of an LED lamp. The brightness of LED lamps is given in lumens. If we compare two LED spots with an identical light output of 600 lumens, according to the data sheet they seem to have the same brightness. However, if both spotlights have different beam angles, about 15° and 60°, this puts the perceived brightness into perspective.

The spotlight with a beam angle of 60° must illuminate a much larger area with the same light output as the 15° spotlight. For this reason, the illuminated surface appears larger but also much darker. The beam angle should therefore always be chosen in conjunction with the desired brightness according to the surface to be illuminated.

Beam Angle Calculator


Please start calculation

Beam Angle Calculator

Please start calculation