title: div content its out of the div when padding is added
body: <p>I have this code </p>
  
  <pre><code>&lt;!DOCTYPE html&gt;
  &lt;html&gt;
  
  &lt;head&gt;
      &lt;meta charset="utf-8" /&gt;
      &lt;meta http-equiv="X-UA-Compatible" content="IE=edge"&gt;
      &lt;title&gt;Page Title&lt;/title&gt;
      &lt;meta name="viewport" content="width=device-width, initial-scale=1"&gt;
      &lt;link rel="stylesheet" type="text/css" media="screen" href="bootstrap/css/bootstrap.min.css" /&gt;
      &lt;link rel="stylesheet" type="text/css" media="screen" href="css/styles.css" /&gt;
  &lt;/head&gt;
  
  &lt;body&gt;
      &lt;div class="container"&gt;
          &lt;div class="form-wrapper"&gt;
              &lt;div class="col-md-6 col-md-offset-3 col-sm-12"&gt;
                  &lt;div class="form-group"&gt;
                      &lt;label for="username"&gt;Usuario&lt;/label&gt;
                      &lt;input type="text" id="username" class="form-control" /&gt;
                  &lt;/div&gt;
              &lt;/div&gt;
              &lt;div class="col-md-6 col-md-offset-3 col-sm-12"&gt;
                  &lt;div class="form-group"&gt;
                      &lt;label for="password"&gt;Contraseña&lt;/label&gt;
                      &lt;input type="password" id="password" class="form-control" /&gt;
                  &lt;/div&gt;
              &lt;/div&gt;
              &lt;div class="col-md-12 text-center"&gt;
                  &lt;button class="btn btn-primary"&gt;Enviar&lt;/button&gt;
              &lt;/div&gt;
          &lt;/div&gt;
      &lt;/div&gt;
      &lt;script src="bootstrap/js/bootstrap.min.js"&gt;&lt;/script&gt;
  &lt;/body&gt;
  
  &lt;/html&gt;
  </code></pre>
  
  <p>and the css</p>
  
  <pre><code>.form-wrapper{
      padding-top: 25%;
      border: 1px solid black;
  }
  </code></pre>
  
  <p>I supposed that the <code>.form-wrapper</code> content its inside the div but when I added the border ,this was the result
  <a href="https://i.stack.imgur.com/MAzGk.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/MAzGk.png" alt="enter image description here"></a></p>
  
  <p>I don't know how the inputs are outside the div boders</p>