Finder shows two dashes instead of folder sizes: the setting that turns them on

In Finder's list view, the Size column shows two dashes for every folder. Finder can show the real sizes; it is simply turned off by default, because adding up a big folder takes time.

Turn on folder sizes

1. Open the folder in Finder and switch to list view (Command 2).
2. Choose View, Show View Options (Command J).
3. Tick Calculate all sizes.
4. Click Use as Defaults to apply it to every folder in list view.

Now click the Size column header to sort largest first.

Why it is slow, and what it misses

• Finder works out each folder's size by adding up every file inside it. A folder with 100,000 small files takes a while.
• Hidden folders, like ~/Library, are not shown unless you press Command Shift . to reveal them. See show hidden files.
• Some app data, such as Mail and Messages, can show as smaller than it is without Full Disk Access.

Faster: Get Info or Terminal

For one folder, select it and press Command I. For a whole list, sorted:

# Everything in your home folder, largest last
du -sh ~/* 2>/dev/null | sort -h

# Including hidden folders and Library
du -sh ~/.[!.]* ~/Library/* 2>/dev/null | sort -h | tail -15

Finder and du can disagree slightly. Finder size versus Terminal size explains why. For the biggest single files rather than folders, see how to find large files.