How to change Cloud Tag sizes

Try adding smallest=16&largest=16 to the code for your tag cloud – changing 16 to whatever size you want to use. I would recommend doing this in a child theme so chnages are not lost with any theme updates. Example:

<?php if ( function_exists( 'wp_tag_cloud' ) ) : ?>

<h2>Popular Tags</h2>
<ul>
<li><?php wp_tag_cloud( 'smallest=16&largest=16' ); ?></li>
</ul>

<?php endif; ?>

More information on the tag cloud: https://codex.www.ads-software.com/Function_Reference/wp_tag_cloud

if you are referring to the tag cloud widget, you will need to use a filter function in functions.php of your child theme;

example code:

add_filter('widget_tag_cloud_args','set_tag_cloud_sizes');
function set_tag_cloud_sizes($args) {
  $args['smallest'] = 16;
  $args['largest'] = 16;
return $args;
}

Thanks Michael! That worked.