Tidy MacThey measure different things. Finder and System Settings show “available” space, which includes purgeable space macOS promises to free later. Terminal’s df shows what’s free right now. Disk Utility lists used, other volumes and free separately. Terminal also uses binary units (GiB), so its numbers look about 7% smaller.
- Note Finder’s “available” number (Finder window status bar or Get Info on Macintosh HD).
- Run df -h / in Terminal to see what’s free right now.
- Open Disk Utility to see used, other volumes and free separately.
- Convert GiB to GB before comparing.
- Thin local snapshots and restart if “available” and free are far apart.
Four numbers, four meanings
| Where | What it shows | Includes purgeable? | Units |
|---|---|---|---|
| Finder (status bar, Get Info) | Available | Yes | GB (decimal) |
| System Settings › General › Storage | Used by category, available | Yes | GB (decimal) |
| Disk Utility | Used, Other Volumes, Free | Shown separately | GB (decimal) |
Terminal df -h / | Free right now | No | GiB (binary) |
Purgeable space: the biggest gap
macOS counts some space as purgeable: Time Machine local snapshots, iCloud files it can remove, and caches. Finder adds that to "available" because macOS promises to free it when an app needs room. Until it does, the space isn't really free, which is why installers can fail while Finder says there's room. Purgeable space explained
GB vs GiB
Finder and System Settings count 1 GB as 1,000,000,000 bytes. Terminal's df -h and du -h count 1 GiB as 1,073,741,824 bytes and print it as "Gi". 500 GB is about 466 GiB. Convert them
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Snapshots hold deleted files
When you delete a file, a Time Machine local snapshot may still reference it. The space returns only when that snapshot is removed, usually within 24 hours, or right away if you thin snapshots yourself. Local snapshots
Clones and shared space
On APFS, copies made in Finder are clones that share blocks. Tools that add up file sizes (including du on folders with clones) can count the same space twice, so folder totals can exceed what's used on the disk.
Which number to trust
For "can I install this?", trust df -h / or Disk Utility's Free. For "how much could I get back?", Finder's available is fair, once purgeable space is released. To release it now:
sudo tmutil thinlocalsnapshots / 999999999999 4Then restart.
Where Tidy Mac fits
Tidy Mac's sizes count APFS clones once and iCloud-only files as zero, and its Home screen shows purgeable space and local snapshots on their own lines, so its totals match Disk Utility and you can see exactly why Finder's number is different. Pricing
Frequently asked questions
Why does my Mac say it has space but won’t install an update?
Finder counts purgeable space as available. The installer needs space that’s free right now. Thin local snapshots and restart. Fix it
Which is more accurate, Finder or Disk Utility?
Both are accurate for what they measure. Disk Utility separates free space from other volumes, so it’s closer to what you can use right now. Finder adds purgeable space.
Why is my free space smaller in Terminal?
Terminal uses GiB (1,073,741,824 bytes) and excludes purgeable space. Finder uses GB (1,000,000,000 bytes) and includes it.
I emptied the Trash but free space didn’t change. Why?
A local snapshot may still hold those files, or Finder hasn’t refreshed yet. Thinning snapshots and restarting usually makes the space show up.