BE SURE YOU ARE COMPARING APPLES TO APPLES

Figuring out storage usage on iOS devices is complicated by the fact that when looking at Storage and storage allocation in Settings > General > About and other sources on the iOS device itself storage is reported in MiB and GiB where Ki = 1,024, but if you look at the same data in iTunes on your Mac or PC it reports in MB and GB where K=1,000 in other words binary v. decimal. For example in Settings > General > About on my iPhone 7 Plus it reports 231.48 GB (more accurately GiB) of available storage while iTunes reports 248.55 GB. Do the math and 231.48 GiB = 248.55 GB. (NOTE; FWIW both iOS and MacOS actually allocate memory and storage using MiB and GiB internally but Apple used to report memory and storage in MiB and GiB but because of a marketing decision several years ago elected to use the arguably less precise MB and GB. I have no idea why they are inconsistent between MacOS and iOS.)

This is a long discussion to explain why when looking at memory and storage numbers in iOS and MacOS it is important to be certain whether the numbers are base 10 or base 2 (binary).

ACTUAL CAPACITY

I am using my iPhone as an example because I have actual data. It is marketed as having a 256 GB storage capacity. Because that is a Marketing nimble I believe it is safe to assume (I know assumptions are risky) that is a decimal (base 10) value and as far as the actual storage allocation goes it is actually 238.42 GiB. The available storage is 231.48 GiB (248.55 GB) which leaves 6.94 GiB (7.45 GB) unaccounted for. My assumption (again I realize the risk of assuming) is that 6.94 GiB is iOS which is completely consistent with what I find on my 64 GB (59.6 GiB) 12" iPad Pro running the same beta version of iOS.

So as Ira said the size of your OS seems to be in the ballpark.

MY WISH LIST: I understand the lack of a Finder function for iOS but I have a few wishes for storage management:
  • Consistent use of GiB or GB between iTunes and Settings (preferably a user selectable option even though only geeks like me would likely know or care)
  • It took way too long and I had to go to far too many places to ferret out the information I reported about storage usage on my iPhone. A single point collection place for all the storage data stored several places in Settings, Tunes, Photos, [b]etc[/I] would be well worthwhile. It doesn't have to offer the ability to delete just present an accurate picture of what is stored and the details. I am surprised there isn't a third party app for this, but the task is more complex than I envision or Apple could be resistant for security reasons(?).
  • Consistent use of GiB or GB between iTunes and Settings (I know I already said this, but it bears repeating.


If we knew what it was we were doing, it wouldn't be called research, would it?

— Albert Einstein