---
title: "OPD ↔ Phase calculator — AperiOptic"
description: "Convert physical optical path difference into phase shift. Free online optics calculator, with the formula and code snippets."
url: "https://aperioptic.com/calculators/opd-phase"
---

# OPD ↔ Phase calculator

Convert physical optical path difference into phase shift.

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

Formula: `Δφ = 2π · OPD / λ (rad)`

## Inputs

| Input | Parameter | Unit | Default |
| --- | --- | --- | --- |
| OPD | `OPD` | nm | 633 |
| Wavelength | `lam` | nm | 633 |

## Result with the default inputs

- Phase: 6.2832 rad
- Phase: 360 °
- Waves: 1

Open it with your own values: put each input in the address as a parameter, for example [`/calculators/opd-phase?OPD=633`](https://aperioptic.com/calculators/opd-phase?OPD=633). A unit other than the listed one goes in `<parameter>_unit`.

Read more: [Wikipedia: Optical path length](https://en.wikipedia.org/wiki/Optical_path_length)

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

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