5s 64gb storage?

[KUPARA]

So why does Apple advertise 64gb when actually it is 57 or 56 gb? storage available..

Wow, either you are a troll or you encounter digital storage for the first time.
Oh well...

 

[LV426]

64gb is raw unformatted decimal based storage

in reality the file system needs to be formatted first, then the OS and computers work in binary and not decimal

64 is a nice round number. Two to the power 6, in fact, which is nice and easy for computers to understand.

When you hear of people talking about KiloBytes, in reality they mean multiples of 1,024 bytes (two to the power 10).

Now, for a 64GB capacity chip, it will have physical address space for two to the power 36 bytes (68,719,476,736). But, since we and computers have got used to 2,4,8,16,32,64 etc. we just call it 64GB.

As others have mentioned, depending on what Apple do internally with the chip, rather less than 68,719,476,736 bytes will be available for 'storage' per se.