functions.php

<?php
/* wp_title() expand
   https://gist.github.com/mcatm/5113723
   ---------------------------------- */

function wp_title_expand($str = null) {

  global $page, $paged;

	$str .= (!$str) ? get_bloginfo('name') : ' - '.get_bloginfo('name');
	$site_description = get_bloginfo('description', 'display');

	if ($site_description && (is_home() || is_front_page())) $str .= ' - '.$site_description;
	if ($paged >= 2 || $page >= 2) $str .= ' - ' . sprintf(__('Page %s'), max($paged, $page));

    	return $str;
}

add_filter('wp_title', 'wp_title_expand');