With the release of WordPress 5.2, came a new tool built into core called “Site Health.” It’s actually pretty awesome and includes a lot of useful data about your WordPress site and server. With it, you can check the size of your WordPress directories and database.
In your WordPress dashboard, browse to “Tools → Site Health → Info.” Under the “Directories and Sizes” tab you’ll find the following info about your site:
WordPress directory size
Uploads directory size
Themes directory size
Plugins directory size
Database size
Total installation size