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# Gigabyte

A gigabyte (symbol GB) is a unit of measurement in computers of one thousand million bytes (the same as one billion bytes in the short scale usage). However, because computers work on the binary system, rather than a gigabyte being 103 megabytes (1000 MBs), the term gigabyte actually means 210 megabytes (1024 MBs).

Because of differences in definition between the standard SI implementation of prefixes and the computer implementations, the exact number in common practice could be either one of the following:

Likewise, a terabyte is either equal to 1024 gigabytes or to 1000 gigabytes depending on the usages.

As a result of this confusion, the unadorned term gigabyte is useful only where just one digit of precision is required. In technical specifications, the first usage is typically expanded to remove the ambiguity ("GB is one billion bytes"). The only exception is RAM, where sizes are always given in the power-of-two units natural to this domain.

Thus, to convert metric gigabytes into binary gigabytes (for example a 100GB drive contains 93GiB when installed), follow this formula:

$\frac{y \cdot 10^9}{2^{30}}$

where y is size of drive in metric gigabytes

megabyte << gigabyte << terabyte

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## Gigabytes in use

As of 2005, most consumer hard drives are measured in gigabyte-range capacities. Per-gigabyte costs are 0.50-0.80 USD.

In speech, gigabyte is often abbreviated to gig, as in "This is a ten-gig hard drive". The initial G in giga- is usually pronounced hard as in geek, not soft as in giant, however both pronounciations are equally valid.

A gigabit, which should not be confused with gigabyte, is 1/8th of a gigabyte and is mainly used to describe bandwidth, e.g. 2 gigabit/s is the speed of current Fibre Channel interfaces.

Unicode has a symbol for Gigabyte: (㎇).

## Distinction between 1000 and 1024 megabytes

Main article: Binary prefix

To clarify the distinction between decimal and binary prefixes, the International Electrotechnical Commission (IEC), a standards body, in 1997 proposed short unions of the International System of Units (SI) prefixes with the word "binary". Thus meaning (2) would be called a gibibyte (GiB). This naming convention has not yet been widely accepted.

## Origin of prefix

The prefix "giga" comes from the Greek word γίγας (gigas) meaning "giant", and was chosen because 109 can be described as a "gigantic" number.