Try it Live

<!DOCTYPE html>
<html>
  <head>
    <title>box-sizing: inherit property</title>
    <style>
     .div1, .div2 {
      background:skyblue;
      width:300px;
      padding:10px;
	  border:2px solid black;
	  margin-bottom:3px;
     }
	 .div1 {
      box-sizing:border-box;
     }	 
     .div2 {
      box-sizing:content-box;
     }	 	 
     .divA {
      background:gray;
      width:200px;
      height:70px;
      box-sizing:inherit;
	  border:1px solid blue;
     }	 
     .divB {
      background:hotpink;
      width:200px;
      height:70px;
      padding:10px;
      box-sizing:inherit;
	  border:1px solid blue;
     }
	 p {
	  background-color:tomato;
	 }	 
    </style>
  </head>
  <body>
    <h3>Here, box-sizing: inherit will acquire box-sizing: border-box</h3>
	<div class="div1">
      <div class="divA"><p>Child divA inside Parent div1</p></div>
      <div class="divB"><p>Child divB inside Parent div1</p></div>
    </div>
	<h3>Here, box-sizing: inherit will acquire box-sizing: content-box</h3>
    <div class="div2">
      <div class="divA"><p>Child divA inside Parent div2</p></div>
      <div class="divB"><p>Child divB inside Parent div2</p></div>
    </div>	
  </body>
</html>