Mac storage stuck on Calculating: how to get the real number in ten seconds

You open System Settings, go to General, then Storage, and the bar says Calculating with a spinner. Five minutes later it still does. Meanwhile the disk is full and you want to know what to delete.

The good news: the free space number does not depend on that screen at all. You can read it right now, and then fix the screen separately.

Get the real number first

Open Terminal (in Applications, then Utilities) and run:

df -h /System/Volumes/Data

# The same answer, as macOS itself reports it
diskutil info / | grep -iE "container (total|free) space"

df reads the volume directly and answers instantly. The Avail column is your free space. On a Mac with macOS Catalina or later, your files live on the Data volume, which is why the command names it rather than /.

Why the bar gets stuck

The total used space is quick to get. The coloured categories are not: macOS has to work out which files are Apps, Documents, Photos and so on, and it leans on the Spotlight index to do that. When the index is being rebuilt, damaged, or turned off, the categories wait, and so does the bar.

Fixes, in the order worth trying

1. Wait ten minutes with the window open. On a large disk the first calculation after a restart is genuinely slow. Leaving and coming back can restart it.
2. Quit System Settings and open it again. Press Command Q, or run killall "System Settings" in Terminal.
3. Free a few GB first if the disk is at zero. Almost nothing on a Mac works well with no free space, including this screen. Empty the Trash, or move one large video to an external drive. Startup disk almost full has quick wins.
4. Restart the Mac. It clears whatever process was holding the calculation.
5. Check whether Spotlight is indexing. Click the magnifying glass in the menu bar and search for anything. If it says it is indexing, let it finish, then try again.
6. Rebuild the Spotlight index. Commands below. It takes from a few minutes to an hour, and searches are incomplete until it is done.
7. Run First Aid. Open Disk Utility, pick your Macintosh HD volume, and click First Aid. It checks for file system errors and repairs what it can.

# Is indexing on for your disk?
mdutil -s /System/Volumes/Data

# Rebuild the index (asks for your password)
sudo mdutil -E /System/Volumes/Data

Rebuilding the index is safe. It deletes nothing of yours, only Spotlight's own record of your files, which it then writes again. How much space that record itself uses is in Spotlight index taking up space.

Finding what to delete while you wait

Even when the bar works, its categories are broad: a single System Data figure can hide 40 GB. The quickest way to see which folders are large in your own home folder is:

du -sh ~/* ~/Library/* 2>/dev/null | sort -h | tail -15

Folders that Terminal cannot read without Full Disk Access, like Photos and Mail, are skipped silently, so the total can look smaller than it is. Storage settings versus a disk analyzer explains the difference, and the storage bar explained covers what each colour means once it loads.