Enter the beam waist (mm) and the wavelength (mm) into the Calculator. The calculator will evaluate the Rayleigh Length. 

Rayleigh Length Formula

Zr = pi * w^2 / l


  • Zr is the Rayleigh Length (mm)
  • w is the beam waist (mm)
  • l is the wavelength (mm)

To calculate Rayleigh Length, multiply pi times the beam waist squared, then divide by the wavelength.

How to Calculate Rayleigh Length?

The following steps outline how to calculate the Rayleigh Length.

  • First, determine the beam waist (mm). 
  • Next, determine the wavelength (mm). 
  • Next, gather the formula from above = Zr = pi * w^2 / l.
  • Finally, calculate the Rayleigh Length.
  • 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.

beam waist (mm) = 80

wavelength (mm) = 90