Terabyte

This redirect is about a measurement term for data storage capacity. For the fictional species, see Terabyte (insect).

Multiple-byte units
Decimal Value Metric 1000 kB kilobyte 10002 MB megabyte 10003 GB gigabyte 10004 TB terabyte 10005 PB petabyte 10006 EB exabyte 10007 ZB zettabyte 10008 YB yottabyte 10009 RB ronnabyte 100010 QB quettabyte	Binary Value IEC Memory 1024 KiB kibibyte KB kilobyte 10242 MiB mebibyte MB megabyte 10243 GiB gibibyte GB gigabyte 10244 TiB tebibyte TB terabyte 10245 PiB pebibyte — 10246 EiB exbibyte — 10247 ZiB zebibyte — 10248 YiB yobibyte — — —
Orders of magnitude of data

A terabyte (derived from the prefix tera- and commonly abbreviated TB) is a measurement term for data storage capacity. The value of a terabyte based upon a decimal radix (base 10) is defined as one trillion (short scale) bytes, or 1000 gigabytes.

A tebibyte (TiB, binary-based terabyte, 2⁴⁰ bytes) is approximately equal to 1.1 (decimal-based) terabytes (10¹² bytes). This difference arises from a conflict between the long-standing tradition of using binary prefixes and base 2 for memory sizes, and the decimal (SI) standard adopted widely both within and outside of the computer industry. Standards organizations such as IEC, IEEE and ISO recommend to use the alternative term tebibyte to signify the traditional measure of 1024⁴ bytes, or 1024 gibibytes, leading to the following definitions:

• According to the SI standard usage, a terabyte (TB) contains 1,000,000,000,000 bytes = 1000⁴ or 10¹² bytes.
• According to binary arithmetic, a terabyte contains 1,099,511,627,776 bytes = 1024⁴ or 2⁴⁰ bytes. Ambiguity can be avoided by using the term "tebibyte" when the binary meaning is intended.

The capacities of computer storage devices are typically advertised using their SI standard values, but the capacities reported by software operating systems uses the binary values.

An NTFS formatted terabyte hard disk or partition in Windows XP shows 931 gigabytes of free, usable storage space (in fact, it is 931 gibibytes).

Terabytes in use

• The U.S. Library of Congress Web Capture team has claimed that "as of May 2008, the Library has collected more than 82.6 terabytes of data".
• Ancestry.com claims approximately 600 terabytes of genealogical data with the inclusion of US Census data from 1790 to 1930.
• LaCie released the world's first 1 TB external hard drive in early 2004.
• Hitachi introduced the world's first one terabyte internal hard drive in 2007.
• In 1993 total Internet traffic was around 100 terabytes for the year. As of June 2008, Cisco Systems estimated Internet traffic at 160 terabytes per second (which equals about 5 Zettabytes for the year).

See also

• Gigabyte
• Petabyte
• Orders of magnitude (data)