# box-sizing: Making Width Mean What You Think

By default a box's width leaves out its padding and border, so it comes out wider than you asked; box-sizing border-box makes the width you write the width you get.

![Cheat sheet: box-sizing: Making Width Mean What You Think](https://fsdtrainingmedia.blob.core.windows.net/public/images/2026/10/76df22a8fd024cdea70934a5bdf9fa1d.webp)

- Category: CSS
- Level: Apprentice
- Tags: Border box, Box sizing, Content box, CSS, web-development, Width
- Updated: November 1, 2026

Source: https://www.ask-codey.com/cheat-sheets/css-box-sizing-cheat-sheet