Minimum Focus Distance Calculator
Calculate magnification ratio and working distance from lens focal length, minimum focus distance, and extension tubes.
Results
Visualization
How It Works
Magnification ratio describes how large the subject appears on the sensor. At 1:1 (1.0x), the subject is the same size as the sensor image, so a full frame sensor captures exactly 36mm of subject width. Extension tubes increase magnification by moving the lens further from the sensor. The added magnification equals the extension length divided by the focal length. Shorter focal lengths gain more magnification per mm of extension but have less working distance.