Post estimated reading time shortcode

functions.php

<?php 


/**
 *
 * Post estimated reading time shortcode
 *
 */
function ns_reading_time_shortcode() {
	$content = get_post_field( 'post_content', $post->ID );
	$word_count = str_word_count( strip_tags( $content ) );
	$readingtime = ceil($word_count / 200);
		if ($readingtime == 3) {
			$timer = " min read";
		} else {
			$timer = " min read";
		}
	$totalreadingtime = $readingtime . $timer;
	return $totalreadingtime;
}
add_shortcode('readingshortcode', 'ns_reading_time_shortcode');