I have a 1.25TB partition that I use for Time Machine backups. When I am in the system preferences for Time Machine on my Mac, it states there's 525GB of 1.25TB available. But when I browse to the partition, there's only two sparse disk image bundles present (one for my wife's laptop and one for mine), and the total size between the two of them is only 83GB. So why does Time Machine think there's already almost 750GB of disk space already being used? Does the Time Machine partition reserve space for future use and adjust the report of available disk space accordingly?


Here's the (relevant) output from df:

Filesystem                                         Size   Used   Avail    Capacity   iused     ifree       %iused  Mounted on
//foobar@Extreme._afpovertcp._tcp.local/TIMACHINE  1.1Ti  764Gi  401Gi    66%        200229312 105076638   66%     /Volumes/TIMACHINE-1
  • If you are comfortable using Terminal.app, can you add the output of "df -h" to your question?
    – Kent
    Jul 20, 2015 at 1:13
  • Thanks for that info. Sometimes, what the Time Machine preference reports is not what the filesystem reports. They appear to be close, although the 401Gi vs 525GB is a little puzzling. Something is taking up the disk space, so the best way to narrow it down is via du -h -d 1 /Volumes/TIMACHINE-1/ which will print the GB used by each folder on that partition. Something may be in the trash, or another hidden (to Finder) directory.
    – Kent
    Jul 21, 2015 at 4:54

1 Answer 1


Time Machine does an incremental backup. Thus it doesn't delete saved filesystem-objects that are changed on the source, but rather adds them up. Time Machine offers an interface that let's you browse through your backup history. You can access it through context-menu of the Time Machine-icon in the menu bar. If it ain't there, you can activate it in the system preferences.

  • The OP already has Time Machine set up. This doesn’t answer or add to the question.
    – forquare
    Jul 20, 2015 at 2:17
  • Yes, that's what I am assimung: The user is already using Time Machine fopr backups. Why wouldn't my answer then? Jul 20, 2015 at 13:54
  • This doesn't help me... my question was regarding the discrepancy between perceived storage used vs presented storage available. I already know how to use Time Machine in general.
    – Bryan
    Jul 20, 2015 at 16:02

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