Enter the angle of incident (deg), the angle of emergence (deg), and the angle of deviation (deg) into the Prism Refraction Angle Calculator. The calculator will evaluate the Prism Refraction Angle. 

Prism Refraction Angle Formula

The following formula is used to calculate the Prism Refraction Angle. 



  • PRA is the Prism Refraction Angle (deg)
  • AOI is the angle of incident (deg) 
  • AOE is the angle of emergence (deg) 
  • AOD is the angle of deviation (deg) 

To calculate the prism refraction angle, add the angle of incident to the angle of emergence, then subtract the angle of deviation.

How to Calculate Prism Refraction Angle?

The following steps outline how to calculate the Prism Refraction Angle.

  1. First, determine the angle of incident (deg).
  2. Next, determine the angle of emergence (deg). 
  3. Next, determine the angle of deviation (deg). 
  4. Next, gather the formula from above = PRA = AOI + AOE – AOD.
  5. Finally, calculate the Prism Refraction Angle.
  6. After inserting the variables and calculating the result, check your answer with the calculator above. 

Example Problem:

Use the following variables as an example problem to test your knowledge.

angle of incident (deg) = 5

angle of emergence (deg) = 6

angle of deviation (deg) = 3

PRA = AOI + AOE – AOD =  ?