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Lens Maker's Equation Focal Length Calculator

1/f = (n−1)(1/R₁ − 1/R₂) — thin lens in air.

Calculates the focal length of a thin lens in air from the refractive index and the radii of curvature of the two surfaces using the lens maker's equation.

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Dr. Helena Ortiz By Dr. Helena Ortiz
Published Last reviewed 1 min read

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How to use this calculator

  1. Fill in the inputs above using the units you already have.
  2. Values update automatically as you type — no submit button needed.
  3. Hover any result row for the underlying formula and intermediate values.

Formula

1/f = (n − 1)·(1/R₁ − 1/R₂)

In depth

Calculates the focal length of a thin lens in air from the refractive index and the radii of curvature of the two surfaces using the lens maker's equation.