The terabyte is a multiple of the unit byte for digital information. The prefix tera represents the fourth power of 1000, and means 1012 in the International System of Units (SI), and therefore one terabyte is one trillion (short scale) bytes. The unit symbol for the terabyte is TB.
1 TB = 1000000000000bytes = 1012bytes = 1000gigabytes.
A related unit, the tebibyte (TiB), using a binary prefix, is equal to 10244 bytes. One terabyte is about 0.9095 TiB. Despite the introduction of these standardized binary prefixes, the terabyte is still also commonly used in some computer operating systems, primarily Microsoft Windows, to denote 1099511627776 (10244 or 240) bytes for disk drive capacity.
One thousand terabytes (1000 TB) is equal to one petabyte (1 PB).
Early usage of terabyte in selected products:
- Optical disk storage 1985
- Supercomputer mass storage: ca. 1992 (decimal usage) 
- Supercomputer memory: 2005 (binary usage)
- Hard disk drives: 2007 (decimal usage)
- Tape drives: 2010 (decimal usage)
- Motherboard memory: 2011 (binary usage) 
Illustrative usage examples
Examples of the use of terabyte to describe data sizes in different fields are:
- Library data: The U.S. Library of Congress Web Capture team claims that as of March 2014[update] "the Library has collected about 525 terabytes of web archive data" and that it adds about 5 terabytes per month ("one terabyte = 1,024 gigabytes").
- Computer hardware: Hitachi introduced the world's first one terabyte hard disk drive in 2007 (1 terabyte = 1,000 gigabytes).
- How operating systems report drive capacity, Seagate Inc.
- "Windows disk space using TB as a binary value, from Seagate.com". Retrieved 16 April 2018.
- Ishigame, Masaaki (12 April 1985). "Optical Document Filing System With Tera-Byte Capacity". International Society for Optics and Photonics. pp. 106–116. doi:10.1117/12.946440. Retrieved 16 April 2018 – via www.spiedigitallibrary.org.
- Vetter, R. J., Du, D. H., & Klietz, A. E. (1992, March). Network Supercomputing: Experiments with a Cray-2 to CM-2 HiPPI Connection. In Heterogeneous Processing, 1992. Proceedings. Workshop on (pp. 87-92). IEEE.
- Gara, et. al., (2005, March/May). Overview of the Blue Gene/L system architecture. IBM JRD, p.195-212 "32 TB of total memory" (p.203)
- "Hitachi Introduces 1-Terabyte Hard Drive". PCWorld. Retrieved 16 April 2018.
- "Tech Jungle: Tech News and Opinions (by Paul Spain)". www.techjungle.com. Retrieved 16 April 2018.
- "New Intel Server Board to Hold 1 TB of RAM". Retrieved 16 April 2018.
- "Web Archiving FAQs: How large is the Library's archive?". Library of Congress. Archived from the original on 31 July 2014. Retrieved 7 April 2011.
- "Hitachi Introduces 1-Terabyte Hard Drive". PC World. 2007-01-07. Retrieved 2008-09-15.