<!DOCTYPE html>
<html>
    <head>
        <meta charset=utf-8>
        <style type="text/css">
            * {
                margin: 0;
                padding: 0;
            }
            .border-box{
                box-sizing: border-box;
                width: 100px;
                height: 100px;
                padding:5px;
                border:5px solid black;
            }
        </style>
    </head>
    <body>
    	<div class="border-box"></div>
    </body>
</html>