By default, WordPress uses the value defined in Settings > Reading to set how many results appear on the search results page. This setting also sets the number of posts per archive page.

You may want this to be different for the search results page, especially if the formatting of the page is different.

Place the following code anywhere in your child theme’s functions.php document. Change the number on line 4 to however many search results per page you’d like to show.

// limit search results per page
function search_results_per_page( $query) {
    if ( $query->is_search() && $query->is_main_query() ) {
        $query->set( 'posts_per_page', '10' );
    }
}
add_filter( 'pre_get_posts', 'search_results_per_page' );