Tebibyte (TiB)
Modern equivalent
1,099,511,627,776 bytes = 1.1 terabytes
Exactly 1,099,511,627,776 bytes, being two to the power of forty, and the binary counterpart to the decimal terabyte.
By the tebibyte the two definitions differ by nearly ten per cent, which at this scale means roughly a hundred gigabytes of apparent capacity. The gap widens by a further two and a half per cent at every step up the ladder, because each binary prefix multiplies by 1,024 where the decimal one multiplies by 1,000, and the small excess compounds. Data centres and storage engineers therefore specify which unit they mean as a matter of routine, since a contract for a hundred terabytes and a contract for a hundred tebibytes differ by about ten terabytes.