Enter the focal length (mm) and the distance between nodal points (mm) into the Minimum Focus Distance Calculator. The calculator will evaluate and display the Minimum Focus Distance.

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## Minimum Focus Distance Formula

The following formula is used to calculate the Minimum Focus Distance.

MFD = FL * 4 + DN

- Where MFD is the Minimum Focus Distance (mm)
- FL is the focal length (mm)
- DN is the distance between nodal points (mm)

To calculate the minimum focus distance, multiply the focal length by 4, then add the distance between modal points.

## How to Calculate Minimum Focus Distance?

The following example problems outline how to calculate Minimum Focus Distance.

Example Problem #1:

- First, determine the focal length (mm).
- The focal length (mm) is given as: 3.25.

- Next, determine the distance between nodal points (mm).
- The distance between nodal points (mm) is provided as: 5.

- Finally, calculate the Minimum Focus Distance using the equation above:

MFD = FL * 4 + DN

The values given above are inserted into the equation below and the solution is calculated:

MFD = 3.25 * 4 + 17 = (mm)

Example Problem #2:** **

For this problem, the variables needed are provided below:

focal length (mm) = 7

distance between nodal points (mm) = 5.5

This example problem is a test of your knowledge on the subject. Use the calculator above to check your answer.

MFD = FL * 4 + DN** = ?**