Enter the focal length (mm) and the crop factor into the Calculator. The calculator will evaluate the Equivalent Aperture. 

Equivalent Aperture Formula

EA =  FL * CF


  • EA is the Equivalent Aperture (in)
  • FL is the focal length (mm)
  • CF is the crop factor

To calculate Equivalent Aperture, multiply the focal length by the crop factor.

How to Calculate Equivalent Aperture?

The following steps outline how to calculate the Equivalent Aperture.

  1. First, determine the focal length (mm). 
  2. Next, determine the crop factor. 
  3. Next, gather the formula from above = EA = FL * CF.
  4. Finally, calculate the Equivalent Aperture.
  5. 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.

focal length (mm) = 3.25

crop factor = 3