Again, that's not it.You've lost more because the larger the disk the more space is lost in the eve whole 1000-1024 marketing thing. See the link I posted above.
16 GB ~= 14.9 GiB
64 GB ~= 59.6 GiB
128 GB ~= 119.2 GiB
Even after you take into account the space used by iOS and pre-installed apps, unavailable capacity not accessible to the user still increases as you go up in size. Space that's just way too large to be accounted for by file system overhead.
Thanks. I think only the OP, terraphantm and you get it.And frankly, that answer is rubbish and I am surprised more people haven't called them out for it.
Pre-installed apps use a different block of memory than the one used to install the core os. Apps like iWork's will not count towards the space used that reduces the storage to 59 gb, so that can't be the reason.
Another 6+ 128GB owner said his reports 114GB capacity. My 6+ 64GB reports 55.7GB.
119.2 actual storage - 114 reported capacity = 5.2 GB
59.6 actual storage - 55.7 reported capacity = 3.9 GB
5.2 - 3.9 GB = 1.3 GB
Can't use the same pre-installed apps excuse here given they have all the same apps.
I checked some jailbreak discussion and it looks like terraphantm's correct. The storage in iOS devices is partitioned into a root and media partition. The root partition is where iOS firmware goes and the size of this partition varies based on the storage capacity of the device. The media partition is the one visible to users and the size of this partition is the one that gets reported in Settings - General - About - Capacity.