title: Why is CSS calc(100%-250px) not working?
body: <p>I've tested it in the most recent versions of Firefox, Chrome, IE 11. In none of those browsers it works when you use the CSS <code>calc()</code> function to calculate e.g. <code>width</code>. As far as I can see I have applied it properly. For reference you might want to check </p>
  
  <blockquote>
    <p><a href="http://www.sitepoint.com/css3-calc-function/" rel="noreferrer">http://www.sitepoint.com/css3-calc-function/</a></p>
  </blockquote>
  
  <p>Why is this not working?</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="false" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-css lang-css prettyprint-override"><code>div {
    background-color: blue;
    height: 50px;
    width: calc(100%-250px);
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div&gt;&lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>
  
  <p>Demos:</p>
  
  <blockquote>
    <p><a href="http://codepen.io/anon/pen/wazZWm" rel="noreferrer">http://codepen.io/anon/pen/wazZWm</a></p>
    
    <p><a href="http://jsfiddle.net/h5mzcow1/" rel="noreferrer">http://jsfiddle.net/h5mzcow1/</a></p>
  </blockquote>
  
  <h1>Edit:</h1>
  
  <p>Yes, this question developed to become a duplicate in the course of many edits, but I still  think this should remain here, because it illustrates the problem better than for example <a href="https://stackoverflow.com/questions/14967421/css-calc-not-working?lq=1">CSS calc() not working</a> . Also, imho the answer is much better.</p>