title: How to set base size for rem
body: <p>I have a simple question, where do you declare the base size that <code>rem</code> is calculated from?</p>
  
  <pre><code>&lt;body&gt;
    &lt;h1&gt;Something&lt;/h1&gt;
  &lt;/body&gt;
  </code></pre>
  
  <p>I can see that the <code>font-size</code> is <code>&lt;body&gt;</code> is set to 16px and the <code>&lt;h1&gt;</code> is set to <code>3rem</code>, yet the font is rendering at 30px when I'd expect 48px.  Can any parent redefine the base?</p>