---
title: "Lens Power (Diopters) calculator — AperiOptic"
description: "Optical power from focal length; combine two thin lenses in contact. Free online optics calculator, with the formula and code snippets."
url: "https://aperioptic.com/calculators/lens-power-diopters"
---

# Lens Power (Diopters) calculator

Optical power from focal length; combine two thin lenses in contact.

Category: [Geometric Optics](https://aperioptic.com/calculators)

Formula: `P = 1/f · P_total = P₁ + P₂`

## Inputs

| Input | Parameter | Unit | Default |
| --- | --- | --- | --- |
| f₁ | `f1` | mm | 100 |
| f₂ (opt.) | `f2` | mm | 200 |

## Result with the default inputs

- P₁: 10 D
- P₂: 5 D
- P total: 15 D
- f total: 66.6667 mm

Open it with your own values: put each input in the address as a parameter, for example [`/calculators/lens-power-diopters?f1=100`](https://aperioptic.com/calculators/lens-power-diopters?f1=100). A unit other than the listed one goes in `<parameter>_unit`.

Read more: [Wikipedia: Optical power](https://en.wikipedia.org/wiki/Optical_power)

[All optics calculators](https://aperioptic.com/calculators)

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The interactive page: https://aperioptic.com/calculators/lens-power-diopters (AperiOptic runs in the browser; free, no account). Every page of the site as Markdown: https://aperioptic.com/llms.txt