Capacity of a Pen drive/External Drive shown on sales pack or on product brochure is differ/less from the storage shown on the computer.
Let us understand mathematics of the bytes in the below chart
1KB is not equal to 1000 Bytes but 1024 Bytes so
1 KB = 1024 Bytes
1 MB = 1024 * 1024 = 1048576 Bytes
1 GB = 1024 * 1024 * 1024 = 1073741824
1 TB = 1024 * 1024 * 1024 *1024 = 1099511627776
But at the time of manufacturing a Pen Drive/External Drive the manufacturer assumes 1kb equals to 1000 Bytes and so on which results in the shortage of space i.e. 1TB to 931 GB. Let us understand with an example.
Suppose a manufacturer made a External Device which have 1,000,000,000,000 Bytes & labeled it with 1 TB .
Simultaneously the computer calculates or sees 1 KB equals to 1024 Bytes but not 1000 Bytes and the actual storage space will be smaller than advertise.
According to the Manufacturer 1 TB = 1000,000,000,000 Bytes
And as we can see above as per computer –
1 GB = 1024 MB
1 MB = 1024 KB
1 KB = 1024 B
So, if we do reverse calculation as per Computer then
1000,000,000,000 bytes Equals to 1000,000,000,000/1024 KB which equals to 976562500 KB.
Similarly, 976562500 KB Equals to 976562500/1024 MB Equals to 953674.32 MB.
And finally, 953674 MB Equals to 953674.32/1024 GB Equals to 931.32 GB.
Hence 1 TB External drive shows the actual storage capacity of 931 GB.