Apple - Why iOS settings and iTunes report the storage usage differently?

I reset my iPhone and recover the backup data. My all installed apps and data are seemingly maintained well, but its storage usage became changed: about 7 GB of new free space came out. Also, it’s reported in the same way by both iTunes and iOS settings.

I’m still not aware of the cause, but my problem was anyway solved.

I have a 4 GB disparity between what shows on my iPhone 6 64 GB and what shows up in iTunes.

I propose that this is because of the iOS Operating System itself. While the phone is able to calculate the exact size of the OS and thus give a more accurate reading, iTunes doesn't have access to that data and assumes your phone just has that much more space.

Here's what you need to do -

  1. If you're jailbroken, those additional files are definitely taking 'hidden' space that's not being accounted for. Think about removing the jailbreak.
  2. If you're using an older iOS version, upgrade. The newer versions (8.1.3 and 8.3) take up less space.
  3. Since you're connected to your iTunes anyways, try doing this - simply load up 1-2 GB of files from your computer to your phone (music/videos/random doc files). This will force your phone to acknowledge the space it actually has.

The last one, of course, is just for science.

I just had this same issue, with a 3GB discrepancy between what iTunes and my iPhone were showing as free space. After looking through "Manage Storage" I realized that iTunes doesn't see the space taken up by downloading music for offline listening through apps like Spotify, but your iPhone does. The numbers matched almost perfectly.

Hope that helps.