How is focal length calculated from distances?

1/f = 1/do + 1/di, so f = (do × di)/(do + di). The focal length is the harmonic mean of object and image distances.

How does field of view relate to focal length?

FOV = 2 × arctan(sensor_size / (2 × focal_length)). A shorter focal length gives a wider field of view.

Focal Length Calculator

Determine the focal length of a lens using multiple methods: from object and image distances, from magnification, or from field of view and sensor size. A versatile tool for optics design.

Inputs

Calculation Method

Object Distance (cm)

Image Distance (cm)

Magnification (absolute)

Field of View (°)

Sensor Size (mm)

Sensor width or diagonal

Results

Focal Length

166.7 mm

Focal Length

16.67 cm

Optical Power

6.00 D

Focal Length Results

Parameter	Value
Focal Length	16.6667 cm (166.67 mm)
Optical Power	6.0000 diopters
Method	Object/Image Distances
Object Distance	50 cm
Image Distance	25 cm
Magnification	0.5000×
Formula	1/f = 1/do + 1/di

Frequently Asked Questions

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