How to Set the Gravatar Size in WordPress

1. Log into the WordPress dashboard and then navigate to 'Appearance.' Click on the 'Editor' link under 'Appearance' to load the theme editing screen. Find the 'comments.php' file for your theme in the right-hand list and then click on its link to load it in the editing box.
2. Find the get_avatar() function in the code of your comments template. This function usually exists between the opening and closing
tags of the template because each comment gets printed out as an item in a numbered list.

3. Add or change the size parameter within the get_avatar() function. Here is an example:
This function requires 'id_or_email,' but size is optional. Use multiples of eight for the best sizes, such as 16-pixels or 32-pixels.
4. Click the blue 'Save' button and then reload your website in the browser. Check that the new size fits with your design and make edits as needed.