Since the release of WordPress 5.2, a new tool called "Site Health" is built into WordPress.
Using Site Health, you can check the size of your WordPress directories and database.
First, login to your WordPress Admin Dashboard.
Next, click on Tools and then Site Health.
Click on Info and then the Directories and Sizes tab where you’ll find the following information about your WordPress site:
- WordPress directory size
- Uploads directory size
- Themes directory size
- Plugins directory size
- Database size
- Total installation size