J515OP
Super Moderator
Here is a handy chart I Googled from a flash memory manufacturer for anybody who wants a reference. Keep this in mind when you see articles proclaiming how much space is taken by apps or OSes or by manufacturers claiming the capacity of their devices.
The manufacturer did not specify the method used to calculate usable capacity but here are the numbers according to standard calculations.
First a key to the numbers.
Decimal (used my manufacturers):
1 G = 10^9 = 1,000,000,000
1 M = 10^6 = 1,000,000
1 K = 10^3 = 1,000
These are the correct prefixes under the SI standards.
Binary (used by the OS for bytes):
1 GiB = 2^30 bytes = 1,073,741,824 bytes
1 MiB = 2^20 bytes = 1,048,576 bytes
1 KiB = 2^10 bytes = 1,024 bytes
These are the correct units for binary though by convention we drop the "i" and use the SI names which leads to the confusion.
The formula to figure actual capacity in GiB is: GB listed * 10^9 / 2^30 = calculated capacity
Calculated capacity - overheard = usable capacity
Note: overhead is inaccessible space on a formatted drive and will very slightly but can be as much as 100 MB
128 GB * 10^9 / 2^30 bytes = ~119.21 GiB
256 GB * 10^9 / 2^30 bytes = ~234.42 GiB
Summary
Using the manufacturer's numbers and the calculated numbers gives us:
1 GB : 0.94 GB stated usable capacity : ~0.93 GiB calculated capacity
2 GB : 1.86 GB stated usable capacity : ~1.86 GiB calculated capacity
4 GB : 3.79 GB stated usable capacity : ~3.73 GiB calculated capacity
8 GB : 7.51 GB stated usable capacity : ~7.45 GiB calculated capacity
16 GB : 15 GB stated usable capacity : ~14.9 GiB calculated capacity
32 GB : 29.7 GB stated usable capacity : ~29.8 GiB calculated capacity
64 GB : 59.53 GB stated usable capacity : ~59.60 GiB calculated capacity
128 GB : no stated usable capacity : ~119.21 GiB calculated capacity
256 GB : no stated usable capacity : ~234.42 GiB calculated capacity
Source: USB Storage | Idol Memory
The manufacturer did not specify the method used to calculate usable capacity but here are the numbers according to standard calculations.
First a key to the numbers.
Decimal (used my manufacturers):
1 G = 10^9 = 1,000,000,000
1 M = 10^6 = 1,000,000
1 K = 10^3 = 1,000
These are the correct prefixes under the SI standards.
Binary (used by the OS for bytes):
1 GiB = 2^30 bytes = 1,073,741,824 bytes
1 MiB = 2^20 bytes = 1,048,576 bytes
1 KiB = 2^10 bytes = 1,024 bytes
These are the correct units for binary though by convention we drop the "i" and use the SI names which leads to the confusion.
The formula to figure actual capacity in GiB is: GB listed * 10^9 / 2^30 = calculated capacity
Calculated capacity - overheard = usable capacity
Note: overhead is inaccessible space on a formatted drive and will very slightly but can be as much as 100 MB
128 GB * 10^9 / 2^30 bytes = ~119.21 GiB
256 GB * 10^9 / 2^30 bytes = ~234.42 GiB
Summary
Using the manufacturer's numbers and the calculated numbers gives us:
1 GB : 0.94 GB stated usable capacity : ~0.93 GiB calculated capacity
2 GB : 1.86 GB stated usable capacity : ~1.86 GiB calculated capacity
4 GB : 3.79 GB stated usable capacity : ~3.73 GiB calculated capacity
8 GB : 7.51 GB stated usable capacity : ~7.45 GiB calculated capacity
16 GB : 15 GB stated usable capacity : ~14.9 GiB calculated capacity
32 GB : 29.7 GB stated usable capacity : ~29.8 GiB calculated capacity
64 GB : 59.53 GB stated usable capacity : ~59.60 GiB calculated capacity
128 GB : no stated usable capacity : ~119.21 GiB calculated capacity
256 GB : no stated usable capacity : ~234.42 GiB calculated capacity
