A terabyte (TB) is 1,024 gigabytes (GB), an allocation of data storage capacity applied most often to hard disk drives. Hard disk drives are essential to computer systems, as they store the operating system, programs, files and data necessary to make the computer work.

In the late 1980s, the average home computer system had a single hard drive with a capacity of about 20 megabytes (MB). By the mid 1990s, average capacity increased to about 80 MBs. Just a few years later, operating systems alone required more room than this, while several hundred megabytes represented an average storage capacity. As of 2005, computer buyers think in terms of hundreds of gigabytes, and this is already giving way to even greater storage.

With the advent of graphic, video and music files, home studios, paint and photo programs, and advanced desktop publishing applications, storage seems to be as wise an investment as real estate. The cost of hard disks has dropped dramatically over the years and continues to do so, even as speed and reliability increase. With the fall in price, more people are installing RAIDs (Redundant Array of Independent Disks) to provide not only storage room, but also redundancy, error-checking, increased performance and backup. A RAID is a series of hard disks working together as a single storage unit. Today a RAID array can easily surpass the 1 terabyte threshold.

To get an idea of the capacity of a terabyte, consider the common megabyte (MB). Just over thousand megabytes equals one gigabyte, but just over one million megabytes equals a terabyte!

1,024 megabytes = 1 gigabyte

1,024 gigabytes = 1 terabyte

1,048,576 (1,024²) megabytes = 1 terabyte

From the opposite extreme, starting at the smallest units of measuring data, it takes an octet, or eight bits, to make one byte. Bits are binary digits of 1 or 0 (ones or zeros). A string of eight makes up the single byte that represents a single character, such as a letter or punctuation mark. Over one trillion bytes, or exactly 1,099,511,627,776 bytes, make up a terabyte, or more than eight trillion bits!

Though the terabyte represents an enormous amount of storage, the petabyte is waiting just beyond. As you may have guessed, the petabyte is made up of 1,024 terabytes.

Tera is Greek for monster, while the word byte was coined in 1956 by Werner Buchholz.