Unable to account for 23.6 GB of disk space I have a 13-inch MacBook Air, and have been using it for about a year now. There are 23.6 GB of memory that appear to be missing from my hard drive. About This Mac -> Storage shows 91GB of files, of which 61GB are "Other": 

The command df -h agrees, showing 91GB used (command output shown below):

    Homes-MacBook-Air:~ BrandonWork$ df -h
Filesystem      Size   Used  Avail Capacity  iused   ifree %iused      Mounted on
/dev/disk1     112Gi   91Gi   21Gi    82% 23864730 5456996   81%   /
devfs          188Ki  188Ki    0Bi   100%      651       0  100%   /dev
map -hosts       0Bi    0Bi    0Bi   100%        0       0  100%   /net
map auto_home    0Bi    0Bi    0Bi   100%        0       0  100%   /home
/dev/disk0s3   620Mi  548Mi   72Mi    89%   140256   18434   88%       /Volumes/Recovery HD
/dev/disk3s2    16Mi  9.8Mi  6.2Mi    62%     2503    1581   61%       /Volumes/Disk Inventory X


However, here the problem arises, as when I examine the disk, only 67.4GB are actually used:


I have six user accounts on this laptop due to my family borrowing it repeatedly, and have run Disk Inventory X on all of them, as I was told that other users' files could account for it, as they are not visible to non-admins. None of them had more than 2GB of files. I have also used OmniDisk Sweeper, with similar results. I have seen all of the following possible problems and solutions, to no avail:


Swap files (they are seen by Disk Inventory X)
Temporary caches (restart your computer; didn't help)
False volumes in /volumes (checked; don't have anything weird there)
Viruses (multiple scans with different programs turn up nothing)


On a previous computer, I had a similar problem with eaten memory; turned out to be WinRAR generating huge .txt files, and these could be found with Disk Inventory X.
Both About this Mac and df seem to agree that you have 91GiB used, 21GiB free on /, which adds up to the volume of your 112GiB (120GB) hard drive.  

The problem must be with the list of files Disk Inventory X scans. 

Run du -s as a superuser starting from / and then going deeper into the filesystem to get a more accurate picture of your disk space usage.  



Keep in mind:
About this Mac and Finder display space in GB (base 10, 1GB = 1000MB)
df -h and du -h show results in GiB (base 2, 1GiB = 1024MiB)
df -H and du -H show results in GB
Many GUI tools display file size in GiB while labeling it as GB