why memories have less capacity than what their name carries? like a 64gb is 58gb when in use

[william_90]

i've two 64gb flash memories and both have 58gb in actual, and when i think about it, i see i just lost 12gb literally which is almost the capacity of a separate flash memory
why developers don't say for example this flash memory has a capacity of 58.443... gb instead of 64 or for other caps like 128 etc

 

[Dereck47]

Flash memory manufacturers, HDD manufacturers, & SSD manufacturers calculate 1 Gigabyte as 1,000,000,000 bytes (Base-10 Numeral System).

Microsoft (and also RAM memory manufacturers) calculate 1 Gigabyte as 1,073,741,824 bytes (Binary Numeral System).

The difference between the 2 methods is approximately 7%.

So whenever you buy Flash memory, or a HDD or SSD, you have to subtract 7% of the advertised capacity to get your actual capacity.