What is a Terabyte?

R. Kayne

A terabyte (TB) is a large 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. Depending on what type of storage is being measured, it can be equal to either 1,000 gigabytes (GB) or 1,024 GB; disk storage is usually measured as the first, while processor storage as the second.

A terabyte is a measurement of storage capacity on a computer's hard drive.
A terabyte is a measurement of storage capacity on a computer's hard drive.

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.

Early on, average home computers held about 20 megabytes; one terabyte is equal to 1,048,576 megabytes.
Early on, average home computers held about 20 megabytes; one terabyte is equal to 1,048,576 megabytes.

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.

Storage space is measured in bytes, which are made up of 8 bits of data. When measuring the number of bytes in a kilobyte (KB) or larger unit, however, there can be differences depending on what standard of measurement is being used. Processor or virtual storage is typically measured using binary:

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!

Disk storage space is usually measured using the International System of Units (SI). By this standard, 8 bits still equal 1 byte, but 1,000 bytes make a KB. This means that a 1 terabyte hard disk holds 1,000 GB or 1012 bytes.

Though the terabyte represents an enormous amount of storage, the petabyte is waiting just beyond. The petabyte is made up of 1,024 (or 1,000) terabytes.

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

A gigabyte can hold the information equivalent of about 1,000 thick books.
A gigabyte can hold the information equivalent of about 1,000 thick books.

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Discussion Comments


Hey 25018! I agree. All hail all bytes!


Hey 79720! Why must you be so picky? A Terabyte is not a caterpillar, OK? This is not Greek to us who like the geekspeak. By the way, Greek is spelled with a capital G. Or do you think you are entering a web address? There is no confusion with us who know what a terabyte is regardless of the origin of the word. OK? relax.


I would like to see the terabyte expressed in the number of, say, hi-def 1020 1-1/2 hour long movies that could be contained in one terabyte.


Is there such a thing that surpasses the petabyte? Someone once asked.

Yeah, It's the "Godlio Byte", the information it can hold is about the size of Earth. The size of the unit is obviously smaller, about the size of a gallon of milk and you can use a simple usb port, and have it stand next to whatever tower you are using now.


Thank you lamaestra for a very succinct, and understandable explanation.


There seems to be complete confusion on this topic, let me explain. A terabyte is from the greek word, terrabis or "of the earth". Terrabytes are a caterpillar type insect, most common in tropical Asia. They are found mostly on the Malaysian peninsula. When dried and crushed, they are used as a garnish on vegetable dishes and in stews.


Your historical stats are off. In the late 80's, "average" home computers were the TV set variety (Commodore, Amiga, TRS-80, etc.) and rarely had hard disks. The limited options were about 10MB, typical business systems (PC's) had much larger capacities (50-120MB).

Mid-90's was Windows 95 era, the average hard drive was about 1GB. And a few years later (~2000) the typical consumer system averaged 30GB.


This is only applicable for storage measurement. For network, 1 KB is 1000 bytes, and so on.


A TB is 1000GB which is 1000MB which is 1000KB which is 1000B which is 8 bits. A TiB is 1024GiB which is 1024MiB which is 1024KiB which is 1024B which is 8 bits.


The only discrepancy is that someone decided to use the term "kilo" (which means one thousand) for 1024 bytes. 1024 is clearly not a "kilo", but it is pretty close, so dang it, it just seems good enough!

1024 is the result of doubling 1 and it's result a number of times - a logical counting method for computers.1,2,4,8,16,32,64,128,256,512,1024...etc


All hail the exabyte!!


Is there such thing that surpasses the petabyte?


My company is looking at purchasing a large number of cameras (44) and the company we are employing for the work is pushing a 6tb server to record the activity from the cameras. We are requesting 30 days of stored video. Is 6tb enough, too much? The video would be run on motion detection to cut down on video with no movement.


Technically, the accurate multiplier is 1,024. But because kilo stands for 1,000 (e.g., a kilometer is 1,000 meters) it is sometimes loosely said that 1,000 bytes equals 1 kilobyte. But technically, this is incorrect. The definition that says kilo is 1,000 is correct when you're talking about decimals. But when you're talking about storage and bytes, you are working within a binary framework, and in the binary world, kilo means 2 to the 10th power, or 1,024.


There seems to be some confusion about the size of these units. Some definitions say that a kilobyte (KB) is 1,000 bytes, a megabyte (MB) is 1000 kilobyte (KB), a gigabyte (GB) is 1000 megabytes (MB), and so on. Other definitions say that a kilobyte (KB) is 1024 bytes, a megabyte (MB) is 1024 kilobytes (KB), etc. Why the discrepancy?

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