| Gigabits (Gbit) | Zebioctets (Zio) |
|---|---|
| 1 Gigabit | 1.05879118407 × 10-13 Zio |
| 2 Gigabits | 2.11758236814 × 10-13 Zio |
| 3 Gigabits | 3.1763735522 × 10-13 Zio |
| 4 Gigabits | 4.23516473627 × 10-13 Zio |
| 5 Gigabits | 5.29395592034 × 10-13 Zio |
| 10 Gigabits | 1.05879118407 × 10-12 Zio |
| 20 Gigabits | 2.11758236814 × 10-12 Zio |
| 25 Gigabits | 2.64697796017 × 10-12 Zio |
| 50 Gigabits | 5.29395592034 × 10-12 Zio |
| 100 Gigabits | 1.05879118407 × 10-11 Zio |
| Reference | Gigabits (Gbit) | Zebioctets (Zio) |
|---|---|---|
| A plain text message (160 characters) | 0.00000128 Gbit | 1.35525 × 10-19 Zio |
| A three-minute MP3 | 0.024 Gbit | 2.5411 × 10-15 Zio |
| A smartphone photo | 0.032 Gbit | 3.38813 × 10-15 Zio |
| A high-definition film | 32 Gbit | 3.38813 × 10-12 Zio |
| A dual-layer Blu-ray disc | 400 Gbit | 4.23516 × 10-11 Zio |
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 zebioctet is a unit of digital information equal to two to the seventieth power octets, which is 1,024 exbioctets. Its symbol is Zio. It is the binary counterpart of the zettaoctet, and the two differ by 18.1 per cent.
Nothing of this size exists. The total quantity of data held by humanity, counting every copy and every backup, is estimated in the low hundreds of zettaoctets, and a zebioctet is 1.18 zettaoctets, so the world holds a few hundred of these units in total. It is the first binary unit for which the world's entire stock is a small multiple rather than a large one.
The unit is defined for completeness rather than for use, which is a deliberate feature of both the metric and the IEC systems. Every prefix applies to every unit without exception, so a reader who has never seen Zio can decode it from the prefix alone. A system that ran out of names at some arbitrary point would force each future user to invent an extension, and rival extensions are how ambiguity is born.
There is one place where the unit would arise naturally. Storage addressing beyond 64 bits has been designed but not needed: the ZFS filesystem uses 128-bit block pointers, giving it a theoretical capacity far beyond any binary prefix that has a name. Where such a scheme states intermediate limits, those limits fall in this range and are properly written in zebioctets.
The 18.1 per cent gap between zebioctet and zettaoctet is worth holding in mind when reading forecasts. Predictions of global data growth are published in zettaoctets, and any that were computed in binary and reported in decimal are nearly a fifth off. Given that such forecasts are already rough, that error is not the largest source of uncertainty, but it is an avoidable one.
The symbol Zio, like all the IEC symbols, is a capital letter followed by lowercase i and then the unit. It is the presence of that i, rather than any statement in the text, that tells a reader unambiguously which quantity is meant, and a document that omits it has not said what it appears to have said.
One zebioctet equals 1,024 exbioctets, 1,180,591,620,717,411,303,424 octets, 8 zebibits, or about 1.181 zettaoctets.