Text Sizes and Font Units


Text size plays a big role in how users read and understand content.

Good font sizing makes websites easy and comfortable to use.

Why Text Size Matters

Correct text size:

  • Improves readability
  • Helps users scan content
  • Makes websites more professional

How CSS Controls Text Size

CSS uses the font-size property to control the size of text.

This sets the paragraph text to a readable size.

Different Units for Font Size

CSS allows you to define text size using:

  • px
  • em
  • rem
  • %

Pixels (px)

Pixels are fixed units.

They give you exact control over text size.

This makes the heading large and clear.

Relative Units

Relative units change size based on other values.

They help make websites more flexible.

em Unit

em is relative to the font size of the parent element.

This makes the text 20 percent larger than its parent size.

rem Unit

rem is relative to the root element font size.

It is more predictable than em.

This makes the heading size consistent across the site.

Percent (%)

Percent is also relative to the parent element size.

This increases the text size slightly.

Which Unit Should You Use

  • Use px for fixed layouts
  • Use rem for scalable designs
  • Use em and % for flexible layouts

Why This Matters for Jobs

Modern websites must work on many screen sizes.

Using proper font units helps build responsive designs.

Common Beginner Mistakes

  • Using very small text sizes
  • Mixing too many units without reason
  • Forgetting accessibility needs

Practice Task

Try this:

  • Set body text using rem
  • Set headings using px
  • Adjust paragraph text using em or %

What You Will Learn Next

In the next lesson, you will learn more about CSS units like px, %, em, and rem in detail.