| Gigabits (Gbit) | Exbioctets (Eio) |
|---|---|
| 1 Gigabit | 1.08420217249 × 10-10 Eio |
| 2 Gigabits | 2.16840434497 × 10-10 Eio |
| 3 Gigabits | 3.25260651746 × 10-10 Eio |
| 4 Gigabits | 4.33680868994 × 10-10 Eio |
| 5 Gigabits | 5.42101086243 × 10-10 Eio |
| 10 Gigabits | 0.00000000108420217249 Eio |
| 20 Gigabits | 0.00000000216840434497 Eio |
| 25 Gigabits | 0.00000000271050543121 Eio |
| 50 Gigabits | 0.00000000542101086243 Eio |
| 100 Gigabits | 0.0000000108420217249 Eio |
| Reference | Gigabits (Gbit) | Exbioctets (Eio) |
|---|---|---|
| A plain text message (160 characters) | 0.00000128 Gbit | 1.38778 × 10-16 Eio |
| A three-minute MP3 | 0.024 Gbit | 2.60209 × 10-12 Eio |
| A smartphone photo | 0.032 Gbit | 3.46945 × 10-12 Eio |
| A high-definition film | 32 Gbit | 0.00000000346945 Eio |
| A dual-layer Blu-ray disc | 400 Gbit | 0.0000000433681 Eio |
The gigabit is a unit of digital information equal to one thousand million bits, or one billion in the short scale. Its symbol is Gbit. It is the unit that names the current standard of wired networking, and the word gigabit has become shorthand for a particular level of capability rather than merely a quantity.
Gigabit Ethernet, standardised in 1998 and 1999, carries one gigabit per second over ordinary twisted-pair copper cabling up to a hundred metres. It replaced the hundred-megabit standard that preceded it and remains the connection built into most computers, switches and routers. That single decision fixed the meaning of gigabit for a generation of engineers.
In octets, a gigabit is 125 megaoctets. A gigabit-per-second link therefore moves about 125 megaoctets each second in ideal conditions, so a two-gigaoctet film transfers in around sixteen seconds. Real transfers are slower because protocol overhead, disc speed and the far end of the connection all impose their own limits, and it is unusual for storage to keep up with the network at these rates.
Domestic fibre services now advertise gigabit speeds routinely, and in many countries the figure has become a marketing threshold rather than a technical one. Very few households can use it: a gigabit connection is enough to stream around two hundred high-definition video services at once. Its real benefit is not peak speed but headroom, since a link that is never near capacity has consistently low latency.
Memory chips are specified in gigabits for the same reason smaller ones are specified in megabits: the count reflects the number of storage cells on the die. An 8-gigabit chip holds one gigaoctet, and eight such chips make an 8-gigaoctet memory module. Flash memory follows the same convention, so a 512-gigabit flash die holds 64 gigaoctets.
Above the gigabit the scale continues in thousands. Ten-gigabit Ethernet is standard in data centres, forty and hundred-gigabit links join buildings and cities, and the backbone of the internet runs at multiples of these. Each step keeps the same relationship to the octet, and each step is quoted in bits per second because that is what the optics and the copper actually carry.
One gigabit equals 1,000,000,000 bits, 1,000 megabits, 125 megaoctets, or about 0.9313 gibibits.
The exbioctet is a unit of digital information equal to two to the sixtieth power octets, which is 1,024 pebioctets. Its symbol is Eio. It is the binary counterpart of the exaoctet, and the two differ by 15.3 per cent.
One number involving this unit is quoted more than any other: sixteen exbioctets, the size of the address space a 64-bit processor can reach. Two to the sixty-fourth octets is 16 EiB, and that figure is the theoretical ceiling on the memory of every machine built on the architecture that has dominated computing since the mid-2000s.
The same limit reappears in filesystems. A filesystem that numbers its blocks with 64-bit values can address 16 exbioctets of blocks, and several modern designs state exactly that as their maximum volume size. Others state 8 exbioctets, having reserved one bit for a sign or a flag — a detail that halves the limit and is worth knowing when reading a specification.
Nothing approaches these sizes in practice. The largest storage systems in the world hold exaoctets, and the total of all data held by humanity is a few hundred zettaoctets, which is tens of thousands of exbioctets. The 64-bit ceiling was chosen precisely so that it would not be reached, and the transition from 32 bits, whose four-gibioctet limit was reached within a decade, is why the designers left so much room.
An exbioctet is 1,152,921,504,606,846,976 bits and 128 pebioctets. It is a quantity that exists in specifications, in address arithmetic and in the design documents of large systems, and nowhere else. Describing it in terms of photographs or films is not useful, because no collection of either comes close.
The symbol Eio and its decimal sibling Eo differ by more than an eighth, which is far too much to leave to inference. When a document writes EB in the context of an address space, it almost certainly means EiB, because address spaces are powers of two by construction; when it writes EB about stored data, it almost certainly means the decimal unit.
One exbioctet equals 1,024 pebioctets, 1,152,921,504,606,846,976 octets, 8 exbibits, or about 1.153 exaoctets.