Enter the focal length (mm) and the crop factor into the Calculator. The calculator will evaluate the Effective Focal Length.

## Effective Focal Length Formula

EFL = FL * CF

Variables:

- EFL is the Effective Focal Length (mm)
- FL is the focal length (mm)
- CF is the crop factor

To calculate Effective Focal Length, multiply the focal length by the crop factor.

## How to Calculate Effective Focal Length?

The following steps outline how to calculate the Effective Focal Length.

- First, determine the focal length (mm).
- Next, determine the crop factor.
- Next, gather the formula from above = EFL = FL * CF.
- Finally, calculate the Effective Focal 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.

focal length (mm) = 50

crop factor = 1.25