add_action( 'pre_get_posts', 'be_change_home_posts_per_page' );
/**
 * Change Posts Per Page for Posts page
 *
 * @author Bill Erickson
 * @link http://www.billerickson.net/customize-the-wordpress-query/
 * @param object $query data
 *
 */
function be_change_home_posts_per_page( $query ) {

	if( $query->is_main_query() && !is_admin() && is_home() ) {
		$query->set( 'posts_per_page', '3' );
		$query->set( 'no_found_rows', true );
	}

}