iCloud & iCloud Photos · iCloud storage space and plans
How do I check how much iCloud storage I have left?
Short answer: Open System Settings → your name → iCloud. The bar shows how much of your iCloud plan is used and by which apps; Manage lets you remove data. That's your account — Storage Profile in Storage Studio shows the Mac side.
Open System Settings, click your name, then iCloud. The bar at the top shows how much of your iCloud plan is used and by what — Photos, iCloud Drive, backups, Messages and so on. Click Manage to see each app's usage and remove data you no longer need.
That figure is about your iCloud account, which is separate from your Mac's own disk. Storage Studio's Storage Profile shows the Mac side: how much space cloud files are actually taking on this Mac, alongside your external drive.
If your account is nearly full, see what to do when iCloud storage is full.