Note that the advertised capacity of storage devices such as harddrives and memory cards assumes 1GB = 1000MB.
But your computer measures 1GB = 1024MB (which is the correct way).
Hence when your computer reports the capacity of the device it will be less than advertised. This is the manufacturers being a bit cheeky.
So in this case;
400 GB x 1000 = 400000 MB
400000 MB / 1024 = 390 GB
The remaining difference is due to the data that comes on the device when you buy it, such as install files etc.
Note that the advertised capacity of storage devices such as harddrives and memory cards assumes 1GB = 1000MB.
But your computer measures 1GB = 1024MB (which is the correct way).
Hence when your computer reports the capacity of the device it will be less than advertised. This is the manufacturers being a bit cheeky.
So in this case;
400 GB x 1000 = 400000 MB
400000 MB / 1024 = 390 GB
The remaining difference is due to the data that comes on the device when you buy it, such as install files etc.