Lensmaker's Equation Calculator
Calculate focal length from lens curvature and refractive index.
This tool is for informational and educational purposes only. It is not a substitute for professional financial, medical, legal, or engineering advice. See Terms of Service.
Can't find what you need?
Request a ToolHow to Use the Lensmaker's Equation Calculator
Enter the refractive index of the lens material and the radii of curvature of both surfaces. Use positive values for convex surfaces and negative for concave. The calculator computes the focal length and optical power.
About Lensmaker's Equation
The lensmaker's equation is fundamental in optical design. It relates a thin lens's focal length to its material properties (refractive index) and geometry (surface curvatures). This equation is used to design eyeglasses, camera lenses, microscope objectives, and telescope optics. Understanding how curvature and material affect focal length is essential for correcting vision, focusing light, and building optical instruments.
Frequently Asked Questions
What is the lensmaker's equation?
The lensmaker's equation relates the focal length of a thin lens to its refractive index and the radii of curvature of its surfaces: 1/f = (n-1)(1/R1 - 1/R2).
What sign convention is used for radii?
R is positive if the center of curvature is on the transmission side of the surface, and negative if on the incidence side. For a standard biconvex lens, R1 is positive and R2 is negative.
What determines if a lens is converging or diverging?
A positive focal length indicates a converging lens. A negative focal length indicates a diverging lens. The sign depends on the curvature and refractive index.