# Sizes and Units

Sizes and Units: Units: px, rem, em, % and Viewport Units.

Updated: November 10, 2026

1. [Units: px, rem, em, % and Viewport Units](https://www.ask-codey.com/lessons/css-units) (Apprentice): Every size in CSS needs a unit, and choosing the right one, px, rem, em, %, vw or vh, decides whether your page grows with the reader's text, fits its space and stays readable.

Source: https://www.ask-codey.com/courses/css-in-depth/topics/css-sizes-and-units