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Here you can Sed posuere consectetur est at lobortis. Donec ullamcorper nulla non metus auctor fringilla. Maecenas sed diam eget risus varius blandit sit amet non magna. Donec id elit non mi porta gravida at eget metus. Praesent commodo cursus magna, vel scelerisque nisl consectetur et.

            
              <header>
  <h1>
    font-size lock<br>
    2em ➡ 4em
  </h1>
</header>
<p>
  This is a font-size calc lock based on <a href="https://blog.typekit.com/2016/08/17/flexible-typography-with-css-locks/">initial work by Tim Brown</a>. Test it by resizing the browser window between 20em and 60em (320px and 960px with default settings) and looking at the title.
</p>
<p>
  This example takes into account that the H1’s parent font-size is <em>not</em> equal to the base font-size, but a bit smaller (85% in this case). So this <code>.85</code> ratio is factored in the calc lock.
</p>
<pre><code>@media (min-width: 20em) and (max-width: 60em) {
  h1 {
    font-size: calc( 2em + 2 * .85 * (100vw - 20rem) / (60 - 20) );
  }
}</code></pre>
<p>
  We also use the <code>rem</code> unit in the equation, and made sure to not redefine the root element’s font-size, so that <code>1rem</code> is equal to the base font-size, matching the values in our media queries. If we had used the <code>em</code> unit, we would have to divide it by <code>.85</code> as well:
</p>
<pre><code>@media (min-width: 20em) and (max-width: 60em) {
  h1 {
    font-size: calc( 2em + 2 * .85 * (100vw - 20em/.85) / (60 - 20) );
  }
}</code></pre>
            
          
!
            
              /* font-size context */
header {
  font-size: 85%;
}

/* font-size calc lock */
h1 {
  font-size: 2em;
}
@media screen and (min-width: 20em) {
  h1 {
    font-size: calc( 2em + 2 * .85 * (100vw - 20rem) / (60 - 20) );
  }
}
@media (min-width: 60em) {
  h1 {
    font-size: 4em;
  }
}

/* Cosmetic styles */
body {
  margin: 1rem;
  line-height: 1.5;
  font-family: Helvetica Neue, Arial, sans-serif;
}
header {
  min-height: 200px;
  margin: 3rem 0;
}
h1 {
  display: table;
  white-space: nowrap;
  margin: 0 auto;
  border: solid 5px;
  padding: .25em .75em .45em;
  font-weight: bold;
  line-height: 1.2;
}
            
          
!
999px
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