---
title: "Strehl Ratio (Maréchal) calculator — AperiOptic"
description: "Approximate Strehl ratio from RMS wavefront error. Free online optics calculator, with the formula and code snippets."
url: "https://aperioptic.com/calculators/strehl-ratio-marechal"
---

# Strehl Ratio (Maréchal) calculator

Approximate Strehl ratio from RMS wavefront error.

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

Formula: `S ≈ exp(-(2π·σ)²)`

## Inputs

| Input | Parameter | Unit | Default |
| --- | --- | --- | --- |
| RMS WFE σ | `sigma` | λ | 0.07 |

## Result with the default inputs

- Strehl: 0.8241
- Diffraction-limited: ✓ yes

Open it with your own values: put each input in the address as a parameter, for example [`/calculators/strehl-ratio-marechal?sigma=0.07`](https://aperioptic.com/calculators/strehl-ratio-marechal?sigma=0.07). A unit other than the listed one goes in `<parameter>_unit`.

Read more: [Wikipedia: Strehl ratio](https://en.wikipedia.org/wiki/Strehl_ratio)

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

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