---
title: "Thermo-Optic Shift (dn/dT) calculator — AperiOptic"
description: "Index change with temperature for the operating environment. Free online optics calculator, with the formula and code snippets."
url: "https://aperioptic.com/calculators/thermo-optic-shift-dn-dt"
---

# Thermo-Optic Shift (dn/dT) calculator

Index change with temperature for the operating environment.

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

Formula: `Δn = (dn/dT) · ΔT`

## Inputs

| Input | Parameter | Unit | Default |
| --- | --- | --- | --- |
| dn/dT (1/K) | `dndt` |  | 0.000011 |
| ΔT | `dT` | K | 20 |
| n at T0 | `n0` |  | 1.5168 |

## Result with the default inputs

- Δn: 2.200000e-4
- n(T): 1.51702

Open it with your own values: put each input in the address as a parameter, for example [`/calculators/thermo-optic-shift-dn-dt?dndt=0.000011`](https://aperioptic.com/calculators/thermo-optic-shift-dn-dt?dndt=0.000011). A unit other than the listed one goes in `<parameter>_unit`.

Read more: [Wikipedia: Thermo-optic effect](https://en.wikipedia.org/wiki/Thermo-optic_effect)

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

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