# Box sizing

Decides whether width includes padding and border.

## What does `box-sizing` do?

`box-sizing` decides whether `width` and `height` include padding and border. `border-box` makes sizes behave the way most people expect.

```css
*, *::before, *::after { box-sizing: border-box; }
```

Level: Apprentice · [More CSS terms at this level](https://www.ask-codey.com/glossary/subjects/css/apprentice)

Updated: September 27, 2026

Source: https://www.ask-codey.com/glossary/box-sizing