boxsize.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .contentbox
        {
            width: 500px;
            height: 100px;
            border: 1px solid blue;
            padding: 20px;
        }
        .borderbox
        {
            width: 500px;
            height: 100px;
            border: 1px solid red;
            padding: 20px;
            box-sizing: border-box;
            overflow: scroll;
        }
    </style>
</head>
<body>
    <div class="contentbox">
        <p>Lorem ipsum paragraph</p>
    </div>
    <div class="borderbox">
        <p>Lorem ipsm paragraph</p>
    </div>
    
</body>
</html>