| Zebioctets (Zio) | Mebibits (Mibit) |
|---|---|
| 1 Zebioctet | 9.00719925474 × 1015 Mibit |
| 2 Zebioctets | 1.80143985095 × 1016 Mibit |
| 3 Zebioctets | 2.70215977642 × 1016 Mibit |
| 4 Zebioctets | 3.6028797019 × 1016 Mibit |
| 5 Zebioctets | 4.50359962737 × 1016 Mibit |
| 10 Zebioctets | 9.00719925474 × 1016 Mibit |
| 20 Zebioctets | 1.80143985095 × 1017 Mibit |
| 25 Zebioctets | 2.25179981369 × 1017 Mibit |
| 50 Zebioctets | 4.50359962737 × 1017 Mibit |
| 100 Zebioctets | 9.00719925474 × 1017 Mibit |
| Reference | Zebioctets (Zio) | Mebibits (Mibit) |
|---|---|---|
| A plain text message (160 characters) | 1.35525 × 10-19 Zio | 0.0012207 Mibit |
| A three-minute MP3 | 2.5411 × 10-15 Zio | 22.8882 Mibit |
| A smartphone photo | 3.38813 × 10-15 Zio | 30.5176 Mibit |
| A high-definition film | 3.38813 × 10-12 Zio | 30517.6 Mibit |
| A dual-layer Blu-ray disc | 4.23516 × 10-11 Zio | 381470 Mibit |
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.
The mebibit is a unit of digital information equal to 1,048,576 bits, which is 1,024 kibibits or two to the twentieth power. Its symbol is Mibit. It is the binary counterpart of the megabit, and the difference between the two has grown to 4.9 per cent — small enough to be ignored casually, large enough to matter in a specification.
Its natural home is semiconductor memory, where capacity is fixed by the address lines on the chip. A memory die with twenty address bits can reach exactly 1,048,576 locations, so densities land on powers of two rather than on round decimal numbers. A chip described as 512 megabits in a catalogue is very often 512 mebibits in reality, which is 537 megabits, and the datasheet is where the truth is written.
That habit is old and deliberate. Semiconductor manufacturers have always sized memory in binary because the wiring makes any other choice wasteful: an address bus is a fixed number of lines, and using only part of the range it can reach throws away silicon. Storage manufacturers had no such constraint, which is precisely why the two industries diverged.
For a sense of quantity, a mebibit is 131,072 octets, or about 128 kibioctets. That is roughly the contents of a long book as plain text, or a single low-resolution image. In network terms it is a hundredth of a second of a gigabit link.
The IEC prefixes were introduced in 1998 partly because at this level and above the approximation stops being safe. Buying a component described as one megabit and receiving one mebibit is a five per cent surprise; at the tebibit the same confusion is a ten per cent surprise, and in a contract for a data centre that is a real sum of money.
Correct usage is now common in standards documents, in hardware datasheets and in operating system internals, and rare in advertising and consumer software. The best rule when reading a figure is to ask which industry produced it: if it describes memory or a chip, assume binary; if it describes storage or a link, assume decimal.
One mebibit equals 1,048,576 bits, 1,024 kibibits, 131,072 octets, or about 1.049 megabits.