I have a 16GB iPad Air 2. I realize the OS takes up some space (on my iPad, "Used" + "Available" only equals 11.9GB), but looking at this screenshot, even my iPad can't accurately explain what's taking up 8.2 GB. I know it's not the OS because Used + Available is already lower than 16. And I added up all the apps underneath and only came to a little under 800MB. What on earth is taking up the remaining 7.5GB?!

My drawing to illustrate my question:

  • you rarely get exactly the amount of storage you pay for, it fluctuates quite bad. take my iphone 64 gb for example, it actually is only 55,5 gb Commented May 26, 2015 at 7:37
  • Thanks, but you're missing my point. The Used + Available definitely don't add up to 16GB. That's the same thing you're saying. But separate from that, look at my Used number in the screenshot I provided, then count up the space I've used in the numbers below. I'm several GB short.
    – MegaMatt
    Commented May 26, 2015 at 11:01
  • Add new picture to clarify my point.
    – MegaMatt
    Commented May 26, 2015 at 11:10
  • it is definitely the os, iOS 8 can take easily 6gb depending on your device, add that to the actual size of a gigabyte versus the advertised size of your storage and it is easy to see why your phone "lost" 7,5 gb. apple is currently facing a lawsuit about this issue as seen here for example: macworld.com/article/2863911/… Commented May 26, 2015 at 11:10

3 Answers 3


This is an excellent summary showing the utility of a periodic erase / install on iOS to let the system reclaim all the space in the filesystem.

One a technical level, SSD storage is made up of multiple cells and there are more complicated storage overhead than a traditional hard drive. This allows for the capacity to not decrease to the user when bad cells are mapped out of service as well as to allow wear leveling. Over time, eventually every storage device will have more and more blocks fail and you would see the same drop off on usable storage. Also, each iOS version uses different amounts of space:

I don't think the combination of OS overhead and bad blocks is the main cause for you, though. Based on your "unaccounted" size, it's likely orphaned files that no longer "belong" to any app.

To test this, make a backup of your iOS data to iCloud and/or to a computer and then restore the device.

Do not add any apps or settings back on the device and repeat the storage measurement. Then you will know if the true capacity was as originally delivered from the factory. If so, all your loss and overhead was filesystem fragmentation, lost files that weren't marked as "belonging" to a specific app.

If you wipe and still have all that space "lost" then it might be technically accurate and a sign the storage doesn't give you the designed capacity and a "repair" would fix it by swapping the device for one with the correct amount of available storage.

  • Yes. I ended up deleting every single non-factory thing from the device that I possibly could and still had many, many gigs of used space. Having exhausted all other options, I contacted Apple and they had me restore it to factory defaults. After bringing it back up, I was back to having only a couple of gigs for OS, with the rest available for use. So that fixed me. Apple should really address this via some sort of utility.
    – MegaMatt
    Commented Jul 23, 2018 at 12:09

These could be some temporary files - usually, after a restart they get deleted freeing precious space.

When you connect iOS device to iTunes, these often show as "other" in Summary tab.

  • Yeah, I suspected that might be the issue, so I restarted, but still had the same issue. This was all before I posted my question.
    – MegaMatt
    Commented May 27, 2015 at 15:05

Some corrupted files might be stuck on you device, and the best option is to start from scratch. Use iTunes to create a backup of your device, restore to the current iOS version, and restore the backup you created.

Check this page for more info about what might steal your precious space.

I have had previous success doing a backup, reset and restore of my device to remove temporary files that are stuck on the device.

  • While this link may answer the question, it is better to include the essential parts of the answer here and provide the link for reference. Link-only answers can become invalid if the linked page changes.
    – grg
    Commented May 27, 2015 at 9:22

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