The Focal Length of a Lens calculator computes the focal length of a lens (f) based on its geometry and material index of the lens and surrounding material.
INSTRUCTIONS: Choose units and enter the following:
(nlens) Refraction Index of Lens Material
(nmedium) Refraction Index of Surrounding Material
(r1) Radius of Curvature of the Lens Toward Light Source
(r2) Radius of Curvature of the Lens Away from Light Source
Focal Length (f): The calculator returns the focal length in meters. However, this can be automatically converted to other length units via the pull-down menu.
The Math / Science
This Lens Maker's Equation1(solved for f) calculates the focal length of a lens given its geometry and surroundings. For more information on and versions of the Lens Maker's Equation, please see the Lens Maker's Equation Calculator page.