Why does 128GB iPhone have 113GB capacity? On the side of the iPhone packaging, Apple defines 1GB as 1,000,000,000 bytes (rather than 1,073,741,824 bytes), so you end up missing 9,438,953,472 bytes (~9GB) calculating it this way for 128GB of space (128,000,000,000 bytes is ~119GB).

My iPhone says that it has 113GB of capacity, but it should be 119GB, so where did the other 6GB disappear to?
The other 6 GB are OS itself. The given capacity is a value for the physical storage that the phone has, not the amount that can be used by the owner. iOS is about 6 GB in size on its own.

Also, the formatted capacity is less than the size of the chips that are manufactured into the device. It's in a very small footnote at the bottom of the tech specs for each iOS device. Typically note #1



As you can see on the following link, each OS differs between versions, device type and device size so the gap in specs to usable space isn't a fixed constant.


How large is iOS?