---
title: "Airy Disk / Diff. Limit calculator — AperiOptic"
description: "Diffraction-limited spot size from wavelength and f/#. Free online optics calculator, with the formula and code snippets."
url: "https://aperioptic.com/calculators/airy-disk-diff-limit"
---

# Airy Disk / Diff. Limit calculator

Diffraction-limited spot size from wavelength and f/#.

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

Formula: `d = 2.4393·λ·N · θ = 1.2197·λ/D (2·j₁,₁/π, j₁,₁/π; ≈ 2.44, 1.22)`

## Inputs

| Input | Parameter | Unit | Default |
| --- | --- | --- | --- |
| Wavelength | `lam` | nm | 550 |
| f-number | `N` |  | 5.6 |
| Aperture | `D` | mm | 100 |

## Result with the default inputs

- Airy disk Ø: 7.5132 µm
- Angular res.: 6.7082 µrad
- Angular res.: 1.3837 arcsec

Open it with your own values: put each input in the address as a parameter, for example [`/calculators/airy-disk-diff-limit?lam=550`](https://aperioptic.com/calculators/airy-disk-diff-limit?lam=550). A unit other than the listed one goes in `<parameter>_unit`.

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

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