It is not uncommon that customers are fooled by the way hard disk capacity is measured, that is different from the way computers measure the same thing. In fact, many people wonder why after installing the disk the total capacity shown by the operating system is lower than expected.
HDD manufacturers define one gigabyte as one billion bytes, whereas the operating system (i.e. the computer) shows the real value. A gigabyte is technically defined as 1.074 billion bytes. The greater the capacity, the higher is the difference between advertised value and actual capacity. For 1 TB disks, the difference is around 10%.
Not all people, however, are happy of this. On a news published at Ars Technica is reported that in 2005 a woman named Sara Cho sued Seagate alleging that the company's use of binary when reporting hard drive sizes constituted false advertising. As reported at Ars Technica:
Seagate has agreed to issue a refund equal to five percent of a drive's original purchase price, provided the hard drive was bought between March 22, 2001 and September 26, 2007. Alternatively, customers can request a free set of Seagate's backup and recovery products (valued at $40).
More detailed information can be read here.
