---
title: "Numerical Aperture calculator — AperiOptic"
description: "NA from acceptance angle, and relation to f/#. Free online optics calculator, with the formula and code snippets."
url: "https://aperioptic.com/calculators/numerical-aperture"
---

# Numerical Aperture calculator

NA from acceptance angle, and relation to f/#.

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

Formula: `NA = n·sin(θ) · N ≈ 1/(2·NA)`

## Inputs

| Input | Parameter | Unit | Default |
| --- | --- | --- | --- |
| Medium n | `n` |  | 1 |
| Half-angle θ | `th` | ° | 15 |

## Result with the default inputs

- NA: 0.2588
- Equiv. f/#: f/1.9319

Open it with your own values: put each input in the address as a parameter, for example [`/calculators/numerical-aperture?n=1`](https://aperioptic.com/calculators/numerical-aperture?n=1). A unit other than the listed one goes in `<parameter>_unit`.

Read more: [Wikipedia: Numerical aperture](https://en.wikipedia.org/wiki/Numerical_aperture)

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

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