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Physics

Lens Optical Power Calculator

Convert signed focal length into optical power in diopters.

SI units shown beside each fieldIdeal model explained below
Physics lab
Physics lab

Use the units beside each input and review the model assumptions.

See the method

Define your system

Runs on your device

Your calculated quantity

Your result

Let’s calculate.

Use the Calculate button to see your result.

Review the method below for assumptions and conventions.

How to use this tool

  1. Enter signed focal length.
  2. Select Calculate to view the result.
  3. Check the method and assumptions below before using the result.

The method, explained

Optical power in diopters = 1/focal length in metres.

A WORKED EXAMPLE

Using signed focal length = 50 cm, the result is 2 D. Change these example inputs to match your task; use the method above to check each step.

Understanding your result

Positive power denotes a converging lens. Thin lenses in contact have approximately additive powers.

What to keep in mind

Positive power denotes a converging lens. Thin lenses in contact have approximately additive powers. An idealized educational model using the stated SI units. Real systems may need additional forces, losses or experimental measurements. Not a safety or equipment specification.

Common questions

How do I use this lens optical power calculator?

Convert signed focal length into optical power in diopters. Enter signed focal length in cm. The starting example is editable; use values for the same system or project.

Which assumptions affect this result?

Positive power denotes a converging lens. Thin lenses in contact have approximately additive powers.

Methodology maintained by ClarityKit. How these tools are built and checked.