WordPress Post reading time without plugin

For Post: Go to wp-content/your-theme/functions.php file and scroll all the way down.

Insert this hook:

/*Post Reading Time count */
if (!function_exists('your_function_name_reading_time')) :
  function your_function_name_reading_time($post_id)
  {
    $content = apply_filters('the_content', get_post_field('post_content', $post_id));
    $read_words = esc_attr(get_theme_mod('global_show_min_read_number', '10'));
    $decode_content = html_entity_decode($content);
    $filter_shortcode = do_shortcode($decode_content);
    $strip_tags = wp_strip_all_tags($filter_shortcode, true);
    $count = str_word_count($strip_tags);
    $word_per_min = (absint($count) / $read_words);
    $word_per_min = ceil($word_per_min);
    if (absint($word_per_min) > 0) {
      $word_count_strings = sprintf(_n(
        '%s min  ',
        '%s min  ',
        number_format_i18n($word_per_min),
        'isha'
      ), number_format_i18n($word_per_min));
      if ('post' == get_post_type($post_id)) :
        echo esc_html($word_count_strings);
      endif;
    }
    if (absint($word_per_min) == Null) {
      echo '1 min';
    }
  }
endif;

Use this function anywhere in your template:

<?php your_function_name_reading_time( get_the_ID() ); ?>