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                <h2>box-sizing: content-box;</h2>
<div class="class">
  Size set to 200x100 pixels with real size 240x140 pixels.
<p><b>Note</b>: If you open Developer Tools, you can see that the real size of the element is <b>240x140</b> pixels. That is beacause we set CSS box model to content-box and browser added padding size value and border size value to the width and height of the element (in this case 2x10 pixels of padding and 2x10 pixels of border).</p>


.class {
  box-sizing: content-box;
  width: 200px;
  padding: 10px; /* this value IS extending size of the element */
  border: 10px solid black; /* this value IS extending size of the element */
  margin: 20px 0;
  line-height: 1.5

/* ====================================================
  Below is code, that is not important for this example 

body {
  font-family: Helvetica;
  padding: 1em 2em;
div {
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  font-size: 16px;

p {
  font-size: 18px;
  margin-top: 2em;
  display: block;
  background: #e8f0fe;
  border: 1px solid #3740ff;
  color: #272eb5;
  padding: 10px 20px;
  line-height: 1.8;