Limit WordPress excerpt length by character and keep last word complete, i.e., instead of 'compat...' show full last word, i.e. 'compatibility...'.

ExcerptLengthByCharacter.php

// Excerpt - Limit Length by Characters and Keep Last Word Complete.
// Solution from:
// https://wordpress.org/support/topic/limit-excerpt-length-by-characters#post-2248039
// ================================================================================

function excerpt_character_length( $excerpt ){
  $permalink = get_permalink($post->ID);
  $excerpt   = get_the_content();
  $excerpt   = preg_replace(" (\[.*?\])",'',$excerpt);
  $excerpt   = strip_shortcodes($excerpt);
  $excerpt   = strip_tags($excerpt);
  $excerpt   = substr($excerpt, 0, 40);
  $excerpt   = substr($excerpt, 0, strripos($excerpt, " "));
  $excerpt   = trim(preg_replace( '/\s+/', ' ', $excerpt));
  $excerpt   = $excerpt . '... <a class="more-link" href="' . $permalink . '">Read More</a>';
  return $excerpt;
}

add_filter('the_excerpt', 'excerpt_character_length');