Show folder sizes in Finder on a Mac, and why they can mislead
· 6 min read
Finder leaves the Size column blank for folders, showing two dashes, because adding up everything inside a folder takes time. To show folder sizes in Finder, switch the window to list view, press Command-J and tick Calculate all sizes. Click Use as Defaults if you want every list view window to do the same.
That is the whole fix for most people. The rest of this guide covers sorting by size, the quicker one-off checks, and why the numbers sometimes refuse to add up.
Turn on folder sizes in list view
- Open a Finder window and choose View, as List (or press Command-2).
- Choose View, Show View Options (Command-J).
- Tick Calculate all sizes.
- To apply this to every folder you open in list view, click Use as Defaults at the bottom of the panel.
Finder starts filling in the Size column straight away. For a folder with a few hundred files the numbers appear almost at once. For your home folder or a large photo archive they arrive one by one, and Finder stays usable while it counts.
If there is no Size column at all, it is switched off in the same panel: tick Size under Show Columns.
Skipping Use as Defaults is the usual reason this seems not to work. Without it, the setting belongs only to the folder you were looking at. You tick the box, open another folder, and the dashes are back.
Sort by size to find what is big
Once sizes are calculated, click the Size column header, and click it again so the largest item is on top. Files and folders sort together, which is what you want when you are hunting for space. Finder’s Keep folders on top setting only applies when sorting by name, so it does not get in the way here.
Then work downward. Open the biggest folder, sort it by size, and repeat until you reach the files themselves. In list view you can also click the disclosure triangle beside a folder to expand it in place, and Option-click the triangle to expand every folder inside it. Each nested folder shows its own size, which makes it easy to spot the one subfolder doing all the damage.
If the goal is the single biggest files on the Mac rather than the biggest folders, a search is faster than walking the tree: Find the largest files on a Mac shows how.
Quicker checks for a single folder
Turning on Calculate all sizes is worth it for a cleanup session. For a one-off question there are faster routes.
- Get Info. Select the folder and press Command-I. After a moment the window shows the size in bytes, the space used on disk, and how many items the folder holds.
- The Inspector. Press Option-Command-I instead. You get one Info window that follows your selection, so you can click from folder to folder and watch the size update without opening a window for each.
- Several folders at once. Select them, hold Control, and open the File menu: Get Info becomes Get Summary Info (Control-Command-I). One window totals the whole selection.
- Free space. View, Show Status Bar puts the item count and the space left on the disk along the bottom of every window. It does not show folder sizes, but it tells you how much room you have while you work.
Column view and gallery view have no Size column. Switch to list view (Command-2) when you are hunting for space, then switch back.
Why the numbers do not always add up
Folder sizes are honest about what is in the folder. They are less honest about what that costs your disk, for a few reasons.
Size and size on disk differ. Get Info shows both. Every file occupies at least one block on the disk, so a folder of thousands of tiny files uses more space than their sizes suggest.
Copies can share storage. On a Mac’s internal drive, duplicating a file creates a clone that shares the same storage as the original until one of them changes. Finder counts each clone at full size. Two folders can each report 10 GB while together they use not much more than 10 GB.
iCloud files may not be on the Mac. With Optimize Mac Storage on, a file kept only in iCloud can show its full size while taking almost nothing locally.
Some folders are off limits. Finder cannot count what it is not allowed to read, such as other users’ home folders, so totals that include them come out low.
Some space lives in no folder you browse. System Data, Time Machine local snapshots and swap files never appear as a folder you can open. If Storage settings says the disk is nearly full and your folders add up to far less, the Mac says storage is full but the folders do not add up walks through where the rest usually is.
The same answer from Terminal
If you would rather have a sorted list than click through windows, two commands do it:
cd ~
du -sh * | sort -h
The first moves to your home folder. The second measures each item in it and prints the results smallest to largest, so the biggest folders end up at the bottom, right above the prompt. The star skips hidden folders, and macOS may ask whether Terminal can read Documents, Desktop or other protected folders. Check disk space from the Terminal with df and du covers the options in more depth.
When you need the whole Mac, not one folder
Finder and du answer “what is in this folder”. The question behind a full disk is usually “what is using the Mac”, and that includes the space no folder shows. System Settings, General, Storage gets you partway there: click the info button beside a category to see the large items in it. System Data, though, stays a single gray bar with no breakdown.
That gap is where Crumb helps. Its audit is read-only and covers the whole Mac, not just your home folder: System Data split into caches, logs, swap, temporary files and leftovers, Time Machine local snapshots on the internal drive, iPhone and iPad backups, and on a shared Mac, which account is using the space. The audit is free forever and changes nothing; you decide afterwards whether anything should go. Crumb runs on macOS 12 Monterey or later.
Questions
Does Calculate all sizes slow the Mac down? On an internal drive it is rarely noticeable. Folders with many thousands of files, network shares and slow external drives are where it drags, because Finder has to visit every file to add them up. Leave it off for those windows. Finder is slow to open a folder with thousands of files covers that case.
I ticked the box and the column still shows dashes. Why? Either Finder is still counting, the folder is one you do not have permission to read, or you are in a different folder from the one you changed. Open View Options again in that window and check the box is ticked there.
Why is the size in Finder different from the one in Storage settings? They measure different things. Finder adds up the files in one folder. Storage settings groups everything on the disk into categories, including space that belongs to no visible folder.