<link href="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">
<script src="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/js/bootstrap.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<div id="controls">
<h1>Download Speed Calculator</h1>
<label for="fsize">File size:</label>
<input type="text" id="fsize" placeholder="File size..." value="1">
<input id="kB" type="radio" name="unit" value="1"><label for="kB">kB</label>
<input id="MB" type="radio" name="unit" value="1000" checked><label for="MB">MB</label>
<input id="GB" type="radio" name="unit" value="1000000"><label for="GB">GB</label>
</div>
<div id="output">
<table id="ttop">
<tbody>
<tr>
<td class="th">Connection Type</td>
<td class="th">Speed</td>
<td class="th">Download Time</td>
</tr>
</tbody>
</table>
<div id="gen"></div>
<table>
<tbody>
<tr style="background: #f0f0f0">
<td><label for="fsize">Custom</label></td>
<td><input type="text" id="csize" placeholder="Speed..."><select id="crate"><option value="1">kbit/s</option><option value="1000" selected>Mbit/s</option><option value="1000000">Gbit/s</option></select></td>
<td id="cout"></td>
</tr>
</tbody>
</table>
</div>