---
title: "Mirror Equation calculator — AperiOptic"
description: "Spherical mirror image distance & magnification. Free online optics calculator, with the formula and code snippets."
url: "https://aperioptic.com/calculators/mirror-equation"
---

# Mirror Equation calculator

Spherical mirror image distance & magnification.

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

Formula: `1/f = 1/do + 1/di`

## Inputs

| Input | Parameter | Unit | Default |
| --- | --- | --- | --- |
| Radius R | `R` | mm | 200 |
| Object dist | `do` | mm | 300 |

## Result with the default inputs

- Focal length: 100 mm
- Image dist: 150 mm
- Magnification: -0.5×

Open it with your own values: put each input in the address as a parameter, for example [`/calculators/mirror-equation?R=200`](https://aperioptic.com/calculators/mirror-equation?R=200). A unit other than the listed one goes in `<parameter>_unit`.

Read more: [Wikipedia: Curved mirror](https://en.wikipedia.org/wiki/Curved_mirror)

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

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