This script function will help you to calculate bandwidth in terms of Kilobyte or Megabyte or Gigabyte.
<form name="test" onSubmit="return tests(test.mailf.value,test.sel.value)">
<input name=mailf type=text>
<select name=sel>
<option value="KB">KB</option>
<option value="MB">MB</option>
<option value="GB">GB</option>
</select>
<input type=submit value=result>
</form>