zebibyte (ZiB)

A zebibyte (ZiB) is a unit used to measure computing and storage capacity. The prefix zebi was created with several others as part of the binary digital capacity measurement system, which is based on powers of two. One zebibyte equals 270 or 1,180,591,620,717,411,303,424 bytes.

The International Electrotechnical Commission (IEC) introduced the binary system prefixes -- kibi, mebi, gibi, tebi, pebi and exbi -- in 1998. It added zebi and yobi in 2005. Before the advent of the binary prefixes, computing and storage capacity were measured using the International System of Units' metric prefixes, which include kilo, mega, giga, tera, peta, exa, zetta and yotta. The SI prefixes are also referred to as the decimal system of prefixes.

Zebibyte in data storage

Before the binary prefixes were developed, the SI prefixes were used to refer to both the power-of-10 multipliers of the decimal capacity measurement system and the power-of-two multipliers of the binary system. The only way to tell which system was being referred to when the term zettabyte (ZB) appeared was to consider the context it was being used in. That term could refer to either 1021 (1,000,000,000,000,000,000,000) bytes or 270 (1,180,591,620,717,411,303,424) bytes.

Today, which system is used often depends on the discipline or industry the speaker works in. The power-of-10 decimal or metric prefixes are mostly used by those in the communications, electronics and physics fields, while IT people usually prefer the power-of-two binary prefixes.

History of the term

In the early days of computing, data storage capacity was significantly smaller than what it is today. When storage capacity was calculated mostly in kilobytes and megabytes, it wasn't a big problem to use the same prefixes to refer to the two different multiplier systems. The differences between the numbers generated by the two systems of measurement were negligible.

For example, one kilobyte (KB) of data storage equals 1,000 bytes using the power-of-10 decimal system. And one KB of data using the power-of-two binary system equals 1,024 bytes. The difference of 24 bytes, or 2.4%, is small enough to be ignored. But data and storage capacity have grown since those early years, and bigger numbers have magnified the difference between the two measurement systems.

Many enterprises are now dealing in terabytes (TB) and even petabytes of data. Using the power-of-10 decimal system, 1 TB of data is equivalent to 1,000,000,000,000 bytes, while a terabyte of data using the power-of-two binary system equals 1,099,511,627,776 bytes. That's a nearly 100 billion-byte, or 10%, difference, which can't be ignored. At even higher levels of capacity, such as zettabytes and yottabytes, the differences between the two measurement systems are even greater.

This TechQuickie video explains why the capacity
of HDDs is sometimes less than advertised.

Back when the same prefixes were used to describe measurements in the decimal and binary systems, one problem in particular cropped up. Hard disk drive manufacturers labeled the capacity of their HDDs using the decimal system. Operating system (OS) vendors didn't follow suit, however, and frequently reported data storage capacity using the binary system. But the same prefixes were used by both sets of vendors, leaving customers confused. A customer might buy an HDD labeled using the decimal system as having 100 gigabytes (GB) of capacity. But when that person put the HDD in their computer, the OS, using the binary system of measurement but the same SI prefix, would report that it had only 93.13 GB of capacity. The customer was rightfully unhappy because it appeared that nearly 7 GB of capacity had disappeared before the HDD was even used.

The development of the IEC standard for the binary system prefixes was meant to eliminate this confusion. Once the new prefixes were in place, the OS vendor in the example above would have used the binary system prefix of gibibyte (GiB) instead of the decimal system GB prefix and would have reported 93.13 GiB instead of 93.13 GB of capacity. The use of the binary prefixes would let the customer know the OS vendor was using a different measurement system from the hard drive manufacturer.

binary and decimal capacity measurement systems

The IEC's intentions were genuinely good in developing the new prefixes. However, they aren't being widely used, and, consequently, haven't solved the data capacity measurement problem. Academics, technical writers and open system developers are those most likely to use the binary prefixes, as they generally aren't used in commercial settings.

How large is a zebibyte?

A zebibyte is the second largest unit in the binary measurement system. A zebibyte is larger than the following binary data capacity measures:

  • A byte -- a ZiB is equal to 1,180,591,620,717,411,303,424 bytes.
  • A kibibyte (KiB) -- a ZiB is equal to 1,152,921,504,606,846,976 KiB.
  • A mebibyte (MiB) -- a ZiB is equal to 1,125,899,906,842,624 MiB.
  • A gibibyte -- a ZiB is equal to 1,099,511,627,776 GiB.
  • A tebibyte (TiB) -- a ZiB is equal to 1,073,741,824 TiB.
  • A pebibyte (PiB) -- a ZiB is equal to 1,048,576 PiB.
  • An exbibyte (EiB) -- a ZiB is equal to 1,024 EiB.

A yobibyte (YiB) is currently the only unit of measure greater than the zebibyte. It's equal to 1,024 ZiB. The EIC and the SI haven't named a unit of measure larger than a yobibyte or yottabyte. The prefix bronto has been suggested as a possible name for the unit following the yottabyte and representing 1027, and the prefix geop has been suggested to represent 1030. However, neither of those prefixes has been officially adopted, and no equivalent binary system prefixes have been suggested.

What zebibytes measure

There aren't any products or systems in use that have zebibytes of capacity. The National Security Agency's U.S Intelligence Community Comprehensive National Cybersecurity Initiative Data Center at Camp Williams near Bluffdale, Utah, is one of the biggest data centers in the world. It was reported that it would have three exabytes (EB) to 12 EB of capacity when completed in 2014.

Given the volume of data growth the world is experiencing, it's only a matter of time before zettabytes and zebibytes become common.

Industry observers in 2009 said one ZB of new data had been created that year. Analyst firm IDC in its 2017 Data Age 2025 report said 16.1 ZB of data was created in 2016 and forecasts that the global data sphere will grow to 163 zettabytes by 2025.

According to IDC, it would take approximately 16 billion of today's largest 12 TB enterprise HDDs to store the 163 ZB data expected to be created in 2025. That means more than 19 ZB of storage capacity across all media types -- HDD, flash, tape, optical and dynamic RAM – must ship from 2017 to 2025 to keep up with that projected storage demand, IDC estimated.

Zebibyte vs. zettabyte and exbibyte

binary system of measurement

As previously mentioned, one zebibyte is equal to 270 1,180,591,620,717,411,303,424 bytes, and one zettabyte is equal to 1021 or 1,000,000,000,000,000,000,000 bytes. A zebibyte is nearly 1.81 ZB.

A zebibyte equals 1,024 EiB. To do the conversion, divide the 1,180,591,620,717,411,303,424 bytes that make up a zebibyte by the number of bytes in an exbibyte, or 1,152,921,504,606,846,976. That gives you 1,024 EiB.

Convert zebibytes to terabytes and exabytes

Each consecutively higher prefix in the binary measurement system has 210, or 1,024, times the number of bytes of the prefix before. Multiply yobibytes times 1,024 to get zebibytes. Multiply zebibytes times 1,024 times to get exbibytes. And multiply exbibytes times 1,024 to get pebibytes and so on.

Here are some examples of how to convert zebibytes to capacity measures that use the decimal measurement system:

  • Zebibytes to terabytes. To convert zebibytes to terabytes, multiply the number of zebibytes in question by the number of bytes in one zebibyte (1,180,591,620,717,411,303,424) and then divide by the number of bytes in a terabyte (1,000,000,000,000). The answer is the terabyte equivalent of that amount of zebibytes.
  • Zebibytes to exabytes. To convert zebibytes to exabytes, multiply the number of zebibytes in question by the number of bytes in one zebibyte (1,180,591,620,717,411,303,424) and then divide by the number of bytes in an exabyte (1,000,000,000,000,000,000). The answer is the exabyte equivalent of that amount of zebibytes.

You can also use one of the many conversion tools available to perform these calculations.

This was last updated in October 2018

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