What a Gigabit?

R. Kayne

A gigabit is a unit of measurement used in computers, equal to one billion bits of data. A bit is the smallest unit of data. It takes eight bits to form or store a single character of text. These 8-bit units are known as bytes. Hence, the difference between a gigabit and a gigabyte is that the latter is 8x greater, or eight billion bits.

USB 3.0 can transfer data at 5 gigabits per second (Gbit/s).
USB 3.0 can transfer data at 5 gigabits per second (Gbit/s).

Storage capacity is normally indicated in bytes rather than bits. You’ll probably not hear someone describe a 200-gigabyte drive as being 1,600 gigabits. Instead, bits are typically used to describe data transfer rates (DTRs), or how fast bits of information can move between devices, such as modems, Firewire, or Universal Serial Bus (USB) ports.

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.

Two types of numerical systems used with computers are the decimal system and the binary system. The decimal system counts the kilo as 1000, while the binary system counts the kilo as 1024. This is because it takes an extra 24 bits of data to store 1000 bits of information on a hard drive or standard storage device. For simplicity, and when referring to data transfer speeds, the more typical designation is the decimal system as follows:

  • 1000 bits = 1 kilobit
  • 1000 kilobits = 1 megabit
  • 1000 megabits = 1 gigabit

  • 1000 bytes = 1 kilobyte
  • 1000 kilobytes = 1 megabyte
  • 1000 megabytes = 1 gigabyte

As an aside, the binary system that uses 1024 bits instead also uses different terminology. The kilobit becomes the kibibit; the megabit, the mebabit; and the gigabit, the gibibit.

Getting back to our more familiar decimal designations, abbreviations can often cause confusion. For example, an Internet provider might advertise speeds of 1500 kbps, while a potential customer might assume the abbreviation refers to kilobytes. Typically, measurements in bytes are used with a capital letter, such as “kBps,” or “KBps.” If all of the abbreviated letters are small case, the reference should be to bits. However, kilobit, megabit and gigabit might also be abbreviated as Kbit, Mbit and Gbit.

The gigabit is not often used in data transmission rates, as most devices push information at slower kilobyte and megabyte speeds. A notable exception is fiber optic cable. In a Verizon press release dated 19 November 2007, the company announced successfully transmitting a video broadcast along fiber optic cable at a whopping 100 gigabits per second (gbps). For comparison, the fastest Ethernet networks have a maximum throughput of 100 megabits per second (mbps). As of winter 2007, Verizon is installing fiber optic service (FiOS) across the U.S. to provide television, digital phone and Internet services.

As technology advances and data transmission rates increase, the average computer user will no doubt become familiar with the gigabit. Until then, most of us will remain locked into slower kilobyte and megabyte speeds, looking forward to jumping that next hurdle.

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Discussion Comments


I've only seen "terabyte" with one "r", "tera-" meaning 1 trillion (American numbering system).















Yes. 1,000 Gigabytes = 1 Terrabyte (decimal system)

or 1,024 Gigabytes = 1 Terrabyte (binary system)


i think 1000 gigabytes(gb)= 1 terrabyte(tb)

i think

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