| Exbioctets (Eio) | Kibibits (Kibit) |
|---|---|
| 1 Exbioctet | 9.00719925474 × 1015 Kibit |
| 2 Exbioctets | 1.80143985095 × 1016 Kibit |
| 3 Exbioctets | 2.70215977642 × 1016 Kibit |
| 4 Exbioctets | 3.6028797019 × 1016 Kibit |
| 5 Exbioctets | 4.50359962737 × 1016 Kibit |
| 10 Exbioctets | 9.00719925474 × 1016 Kibit |
| 20 Exbioctets | 1.80143985095 × 1017 Kibit |
| 25 Exbioctets | 2.25179981369 × 1017 Kibit |
| 50 Exbioctets | 4.50359962737 × 1017 Kibit |
| 100 Exbioctets | 9.00719925474 × 1017 Kibit |
| Reference | Exbioctets (Eio) | Kibibits (Kibit) |
|---|---|---|
| A plain text message (160 characters) | 1.38778 × 10-16 Eio | 1.25 Kibit |
| A three-minute MP3 | 2.60209 × 10-12 Eio | 23437.5 Kibit |
| A smartphone photo | 3.46945 × 10-12 Eio | 31250 Kibit |
| A high-definition film | 0.00000000346945 Eio | 31250000 Kibit |
| A dual-layer Blu-ray disc | 0.0000000433681 Eio | 390625000 Kibit |
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.
The kibibit is a unit of digital information equal to 1,024 bits. Its symbol is Kibit. It is the first of the binary prefixes, a set of units defined by the International Electrotechnical Commission in 1998 to end a confusion that had run through computing since the 1960s.
The problem was straightforward. Computers address memory in powers of two, so memory came in chunks of 1,024 rather than 1,000. Engineers borrowed the metric prefix kilo for that quantity because 1,024 is close to 1,000, and for small numbers the approximation was harmless. But storage and transmission counted in true thousands, so the same prefix meant two different things depending on which part of the machine was being described.
The IEC's solution was to coin new names. Kibi is a contraction of kilo binary, and the pattern continues with mebi, gibi, tebi, pebi, exbi, zebi and yobi. Each is 1,024 times the one below, and each symbol takes the form of a capital letter followed by a lowercase i: Ki, Mi, Gi, Ti and so on. The kilobit then means one thousand bits and nothing else.
A kibibit is 128 octets, and the gap from a kilobit is 2.4 per cent. That small difference is why the two were confused for so long: at this scale nobody notices. The error compounds by 2.4 per cent at every step, reaching 5 per cent at the mebibit, 7 per cent at the gibibit and 21 per cent by the yobibit, which is where the ambiguity became genuinely expensive.
Adoption has been partial and uneven. Standards bodies, the Linux kernel and most technical documentation use the IEC prefixes correctly. Consumer software largely does not, and many programs still write KB while dividing by 1,024. The result is that a reader must often infer from context which convention a number follows, which is exactly what the standard was written to prevent.
In practice the kibibit itself appears mainly in the specifications of small memory chips, in serial memory used by embedded systems, and in protocol documents where an exact power of two matters. Anywhere the number 1,024 is meant rather than 1,000, this is the correct unit.
One kibibit equals 1,024 bits, 128 octets, or 1.024 kilobits.