---
title: "Knife-Edge Beam Profile calculator — AperiOptic"
description: "1/e² Gaussian beam radius from 10–90% (or 16–84%) knife-edge sweep. Free online optics calculator, with the formula and code snippets."
url: "https://aperioptic.com/calculators/knife-edge-beam-profile"
---

# Knife-Edge Beam Profile calculator

1/e² Gaussian beam radius from 10–90% (or 16–84%) knife-edge sweep.

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

Formula: `w = Δx / k (k = √2·erf⁻¹(1 − 2p): k₁₀₋₉₀ = 1.2816, k₁₆₋₈₄ = 0.9945)`

## Inputs

| Input | Parameter | Unit | Default |
| --- | --- | --- | --- |
| Δx (10→90) | `dx` | µm | 100 |
| Δx (16→84) | `dx2` | µm | 64 |

## Result with the default inputs

- w (10–90): 78.0304 µm
- w (16–84): 64.3567 µm
- FWHM (10–90): 91.8738 µm

Open it with your own values: put each input in the address as a parameter, for example [`/calculators/knife-edge-beam-profile?dx=100`](https://aperioptic.com/calculators/knife-edge-beam-profile?dx=100). A unit other than the listed one goes in `<parameter>_unit`.

Read more: [Wikipedia: Beam diameter, Knife-edge](https://en.wikipedia.org/wiki/Beam_diameter#Knife-edge)

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

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