Get the estimated reading time of an article, blog post, or custom post in WordPress

get_estimated_reading_time.php

<?php

/**
 * get_estimated_reading_time --- Get estimated reading time in minutes
 * @author Vincent V. Toscano
 * Created by Vincent on Oct. 19, 2020
 * Updated Oct. 20, 2020
 * Ref.: get_the_content https://developer.wordpress.org/reference/functions/get_the_content/
 * Ref.: strip_shortcodes https://developer.wordpress.org/reference/functions/strip_shortcodes/
 * Ref.: strip_tags https://www.php.net/manual/en/function.strip-tags.php
 * @param   string $content Feed the method your copy/content/string
 * @param   int $wpm Typical/average words per minute 200 to 400 wpm
 * @return  false|float
 * @example <?php $readTime = get_estimated_reading_time( get_the_content() ); ?>
 *          <time datetime="P<? echo $readTime?>M"><? echo $readTime?> minute<?php if ($readTime > 1)echo 's'; ?></time>
 */
function get_estimated_reading_time( $content = '', $wpm = 250 ) {
	$cleaned_content = strip_tags( strip_shortcodes( $content ) );
	$word_count = str_word_count( $cleaned_content );
	$time = ceil( $word_count / $wpm );
	return $time;
}

Updated comment and example to use echo