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A look at the ch CSS unit

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What is the ch unit in CSS and how to use it

27 Nov, 2021 Β· 3 min read

A while ago, I wrote about the [Tailwind typography plugin]. I was blown away by how easy and readable big text elements become.

After researching their applied styles, I've noted the prose class goes off on the ch unit.

.prose {
  max-width: 65ch;
}

This is based on the width of the 0 characters for a specific font! Yes, so changing the font might affect this.

And the result is that it makes a super readable width.

Seeing the ch unit in action

Let's give this a try and make a demo with it.

For the HTML, we render two sections with different classes to represent the different fonts.

<section class="georgia">
  <p>copy</p>
</section>
<section class="helvetica">
  <p>copy</p>
</section>

Let's add some basic styling to see these two sections under each other.

body {
  min-height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  flex-direction: column;
  margin: 0;
}
section {
  display: flex;
  align-items: center;
}
p {
  max-width: 65ch;
}
.georgia {
  font-family: Georgia, serif;
}
.helvetica {
  font-family: helvetica, sans-serif;
}

As you can see, we use the same max-width value for both elements, but once we know the result, the one is bigger.

CSS ch unit in action

The image above shows that the top element rendering the Georgia font is wider. This is caused by its 0 (zero) being wider than the Helvetica font set.

You can also have a play with it yourself in this Codepen.

See the Pen Untitled by Chris Bongers (@rebelchris) on CodePen.

Extra reading

Shawn wrote this great article using this ch unit and just 100 bytes of CSS to make anything look great!

Here are his magic bytes:

html {
  max-width: 70ch;
  padding: 3em 1em;
  margin: auto;
  line-height: 1.75;
  font-size: 1.25em;
}

You can read the full article on Shawn's blog.

To wrap this up, the ch unit is super powerful, yet a bit unpredictable as the size might change.

I like it, as I don't do static pixel design anyway, but I'm looking forward to hearing your thoughts on the ch unit!

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