The following code shows how to change Buttons Sizes.
<!DOCTYPE html>
<html lang="en">
<head>
<link rel="stylesheet"
href="http://netdna.bootstrapcdn.com/bootstrap/3.0.3/css/bootstrap.min.css">
<link rel="stylesheet"
href="http://netdna.bootstrapcdn.com/bootstrap/3.0.3/css/bootstrap-theme.min.css">
<script type="text/javascript"
src="http://code.jquery.com/jquery.min.js"></script>
<script
src="http://netdna.bootstrapcdn.com/bootstrap/3.0.3/js/bootstrap.min.js"></script>
<style type="text/css">
.bs-example {<!-- ww w.j a v a 2 s . c om-->
margin: 20px;
}
</style>
</head>
<body>
<div class="bs-example">
<button type="button" class="btn btn-default btn-lg">Default</button>
<button type="button" class="btn btn-primary btn-lg">Primary</button>
<button type="button" class="btn btn-info btn-lg">Info</button>
<button type="button" class="btn btn-success btn-lg">Success</button>
<button type="button" class="btn btn-warning btn-lg">Warning</button>
<button type="button" class="btn btn-danger btn-lg">Danger</button>
<hr>
<button type="button" class="btn btn-default">Default</button>
<button type="button" class="btn btn-primary">Primary</button>
<button type="button" class="btn btn-info">Info</button>
<button type="button" class="btn btn-success">Success</button>
<button type="button" class="btn btn-warning">Warning</button>
<button type="button" class="btn btn-danger">Danger</button>
<hr>
<button type="button" class="btn btn-default btn-sm">Default</button>
<button type="button" class="btn btn-primary btn-sm">Primary</button>
<button type="button" class="btn btn-info btn-sm">Info</button>
<button type="button" class="btn btn-success btn-sm">Success</button>
<button type="button" class="btn btn-warning btn-sm">Warning</button>
<button type="button" class="btn btn-danger btn-sm">Danger</button>
<hr>
<button type="button" class="btn btn-default btn-xs">Default</button>
<button type="button" class="btn btn-primary btn-xs">Primary</button>
<button type="button" class="btn btn-info btn-xs">Info</button>
<button type="button" class="btn btn-success btn-xs">Success</button>
<button type="button" class="btn btn-warning btn-xs">Warning</button>
<button type="button" class="btn btn-danger btn-xs">Danger</button>
</div>
</body>
</html>