Why is 2 TB only 1.8 TB ??

Drive that is advertised as a 2000 Gbyte actually contains 2.000.000.000.000 bytes

2.000.000.000.000 / 1024 = 1953125000 kb
1.953.125.000 / 1024 = 1907348,63 Mb
1907348,63 / 1024 = 1862,64 Gb
1862,64 / 1024 = 1,818984375 Tb

2.000.000.000.000/1024/1024/10­24/1024 = 1,81T

That’s why its only 1.81TB

More Information

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1 Gbyte = 1024 Mbyte,
1 Mbyte = 1024 Kbyte
1 Kbyte = 1024 byte