# Convert a Lab color to an LCH color

Turn a and b into chroma and hue degrees.

Canonical: https://1loc.dev/misc/convert-a-lab-color-to-an-lch-color/
Version: 1.0.0
Runtime: JavaScript · Node.js 22 / modern browsers
Verification: Local fixtures; no external services
Updated: 2026-10-28

## Implementation

```javascript
function labToLch([l, a, b]) { return [l, Math.hypot(a, b), ((Math.atan2(b, a) * 180) / Math.PI + 360) % 360]; }
```

## Input

```json
[
  52,
  40,
  30
]
```

## Expected output

```json
[
  52,
  50,
  36.86989764584405
]
```

## Edge case

Input:
```json
[
  50,
  0,
  -10
]
```
Output:
```json
[
  50,
  10,
  270
]
```

## Limits

- Hue is normalized to 0–360°; the original could return negative hues, as the edge case would.
- Assumes CIE Lab input; it does not convert from sRGB.

The lab validates types and size before calling this function. Add equivalent validation at your own trust boundary.

## Source and license

Original: https://github.com/phuocng/1loc/blob/14b481cf60dff1620ab1bb99a43b1f68068cdd9b/contents/convert-a-lab-color-to-an-lch-color.mdx
Author: Nguyen Huu Phuoc and original contributors
Contributors: See original repository history
Source commit: 14b481cf60dff1620ab1bb99a43b1f68068cdd9b
Copyright (c) 2020 phuoc-ng
License: MIT — https://1loc.dev/licenses/
Maintainer: Oveyon
Modifications: Uses Math.hypot and normalizes hue to 0–360 degrees. Original MDX retained as inert source evidence.