Edit in JSFiddle

<html>
  <head>
    <title></title>
  </head>
  <body>
    <div id="pai">
      <div id="filha">

      </div>

    </div>
   
  </body>
</html>


html, body { height: 100%;}
#pai{
  height:60%;
  background: red;
  padding-top: 5%;
}
#filha{
  height: 50%;
  background: blue;
  
}