CSS - Measurement Units

 <!DOCTYPE html>
<html>
<head>
  <title>CSS Units</title>
  <style>
    .text-2em {
      font-size: 2em;
    }
    
    .text-3em {
      font-size: 3em;
    }
    
    .text-4em {
      font-size: 4em;
    }
  </style>
</head>
<body>
  <h1 class="text-2em">This is a heading with font-size 2em</h1>
  <p class="text-3em">This is a paragraph with font-size 3em</p>
  <span class="text-4em">This is a span with font-size 4em</span>
</body>
</html>

CSS - Measurement Units

Example -Demo em unit