# Definite size

A size known without laying out the contents.

## What is a **definite size**?

A **definite size** is one the browser can work out without laying out the contents, like `300px` or `50%` of a fixed-size parent.

```css
.panel { height: 400px; }
.panel .inner { height: 50%; }   /* works: 50% of a definite height */
```

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

Updated: September 27, 2026

Source: https://www.ask-codey.com/glossary/definite-size