Limit the Character Length of the Content or Excerpt in WordPress

And this to your functions file…

function custom_content_length($content) {
	return mb_strimwidth($content, 0, 300, '...');	//cuts the string at 300 characters and closes it with ...
}

As a function, this can easily be used site-wide and is adjustable in one central place (in your functions file). Simply adjust the character limit to suit your needs.

Next, call your excerpt/content like so…

$content = get_the_excerpt();
echo custom_content_length($content);

This code will pass your excerpt/content onto the function, which cuts the string length and adds 3 dots to the end (but only if it exceeds 300 characters), before returning the newly formatted output for you to echo on screen.

This is a great technique to use on archive and category-based pages.