Lensmaker Equation Calculator

Enter value and click on calculate. Result will be displayed.

1/f = ( n1/nm - 1 ) ( 1/r1 - 1/r2)
p=1/f
f = Focal Point
nl = Refractive Index of Lens Material
nm = Refractive Index of Ambient Medium
r1 = Radius of Curvature of the First Surface
r2 = Radius of Curvature of the Second Surface
P = Lens Power

Radius of Curvature of the First Surface:
Cm
Radius of Curvature of the Second Surface:
Cm
Refractive Index of Lens Material:
m
Refractive Index of Ambient Medium:
m
Focal Point:
Cm
Lens Power:
Diopters

The Lensmaker’s Equation Calculator is a tool that helps calculate the focal length of a lens based on its physical properties, like the curvature of its surfaces and the refractive index of the lens material.

What is the Lensmaker’s Equation?
The equation is:

Where:

  • = focal length of the lens
  • = refractive index of the lens material
  • = radius of curvature of the first lens surface
  • = radius of curvature of the second lens surface
  • = thickness of the lens between the two surfaces (can often be approximated as zero for thin lenses)

For thin lenses, the equation simplifies to:

Why use the Lensmaker’s Equation?
This equation is essential for designing lenses in optics. It helps predict how light will converge or diverge when passing through the lens. It’s widely used in:

  • Camera lenses
  • Glasses and contact lenses
  • Microscopes and telescopes

How does a Lensmaker’s Equation Calculator work?
The calculator simplifies the math — you just input:

  • The refractive index ()
  • The curvature radii of the lens surfaces (R1 and R2)
  • (Optional) the lens thickness ()

The calculator applies the formula and outputs the lens’s focal length ().

When would you use it?

  • When designing or analyzing an optical system
  • To choose the right lens for a camera or scientific device
  • In physics or engineering courses involving optics