# Convert the name of an Excel column to a number

Read a column name as a base-26 number where A is 1.

Canonical: https://1loc.dev/string/convert-the-name-of-an-excel-column-to-number/
Version: 1.0.0
Runtime: JavaScript · Node.js 22 / modern browsers
Verification: Local fixtures; no external services
Updated: 2026-10-28

## Implementation

```javascript
function columnNumber(column) { return column.split('').reduce((total, letter) => total * 26 + parseInt(letter, 36) - 9, 0); }
```

## Input

```json
"AB"
```

## Expected output

```json
28
```

## Edge case

Input:
```json
"a"
```
Output:
```json
1
```

## Limits

- The lab accepts 1–6 letters (up to ZZZZZZ). Lowercase letters work too.

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-the-name-of-an-excel-column-to-number.mdx
Source file (this edition): https://github.com/akamind/1loc/blob/0a77f131b22d2ba3b7ec1728846f900c22821678/contents/convert-the-name-of-an-excel-column-to-number.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: Validates 1–6 letters so the result stays within the lab's numeric bounds. Original MDX retained as inert source evidence.