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Free lens focal length calculator for optics and imaging tasks. Compute focal length, optical power (diopters), and magnification from object and image distances.
Last updated: April 20, 2026
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Focal length
0.2000 m
Optical power
5.0000 D
Magnification m = -di/do
-2.0000
Interpretation
Estimated focal length is 0.2000 m and optical power is 5.0000 D.
Equation:
1/f = 1/do + 1/di
Formula
1/f = 1/do + 1/di
Relation
P = 1/f
Relation
m = -di/do
do = 0.30 m, di = 0.60 m
Focal length
0.2000 m
Optical power
5.0000 D
The calculator applies the thin-lens equation to connect object distance, image distance, and focal length. It also reports optical power and magnification for practical lens analysis.
1/f = 1/do + 1/diP = 1/fm = -di/doUse consistent units for distances; this implementation assumes meters for direct diopter conversion.
Share it with optics students, photographers, and engineers.
Suggested hashtags: #Optics #Lens #FocalLength #Physics #Calculator