---
title: "Beer–Lambert Law calculator — AperiOptic"
description: "Transmittance through an absorbing medium. Free online optics calculator, with the formula and code snippets."
url: "https://aperioptic.com/calculators/beer-lambert-law"
---

# Beer–Lambert Law calculator

Transmittance through an absorbing medium.

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

Formula: `T = 10^(-α·L·c)`

## Inputs

| Input | Parameter | Unit | Default |
| --- | --- | --- | --- |
| α (abs.) | `a` | L/mol·cm | 1000 |
| Path | `L` | cm | 1 |
| Conc. | `c` | mol/L | 0.001 |

## Result with the default inputs

- Absorbance A: 1
- Transmittance: 10 %
- OD: 1

Open it with your own values: put each input in the address as a parameter, for example [`/calculators/beer-lambert-law?a=1000`](https://aperioptic.com/calculators/beer-lambert-law?a=1000). A unit other than the listed one goes in `<parameter>_unit`.

Read more: [Wikipedia: Beer–Lambert law](https://en.wikipedia.org/wiki/Beer%E2%80%93Lambert_law)

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

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