---
title: "Retardation ↔ Phase Shift calculator — AperiOptic"
description: "Convert waveplate retardation in nm to phase and wavelength fraction. Free online optics calculator, with the formula and code snippets."
url: "https://aperioptic.com/calculators/retardation-phase-shift"
---

# Retardation ↔ Phase Shift calculator

Convert waveplate retardation in nm to phase and wavelength fraction.

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

Formula: `φ = 2π · Γ/λ (rad)`

## Inputs

| Input | Parameter | Unit | Default |
| --- | --- | --- | --- |
| Retardation Γ | `Gamma` | nm | 137.5 |
| Wavelength λ | `lam` | nm | 550 |

## Result with the default inputs

- λ fraction: 0.25 λ
- Phase: 90 °
- Phase: 1.5708 rad

Open it with your own values: put each input in the address as a parameter, for example [`/calculators/retardation-phase-shift?Gamma=137.5`](https://aperioptic.com/calculators/retardation-phase-shift?Gamma=137.5). A unit other than the listed one goes in `<parameter>_unit`.

Read more: [Wikipedia: Waveplate](https://en.wikipedia.org/wiki/Waveplate)

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

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