You can paste this block of code in your currently active WordPress theme functions.php
file:
function wpse_footer_db_queries(){
echo '<!-- '.get_num_queries().' queries in '.timer_stop(0).' seconds. -->'.PHP_EOL;
}
add_action('wp_footer', 'wpse_footer_db_queries');
The above block of code, will render an HTML comment in the footer of your theme (before </body>
and </html>
, containing the number of database queries and how log they took to retrieve.