This is very useful to check when you're close to your plan's limit. Sometimes the account is just full with backups or emails in the trash and we can just eliminate files instead of upgrade to a more expensive plan.
Login to cPanel and click on "Disk Usage" under the FILES section
This tool is updated every 4 hours, then the results might not be accurate if you're making modifications in real time.
This tool offers an overview of the space consumption of every folder. For this tutorial we are using a newly created account, so most of the folders are not using much space.
If we scroll down a bit more we see see additional details. Every folder has an arrow, that when clicked shows us its subfolders. Clicking on the folder name will open the filemanager.
Analysing the public_html directory (the one using most of the space) and inside it we see that the uploads folder is using more than 280MB