| Tebibits (Tibit) | Exbioctets (Eio) |
|---|---|
| 1 Tebibit | 0.000000119209289551 Eio |
| 2 Tebibits | 0.000000238418579102 Eio |
| 3 Tebibits | 0.000000357627868652 Eio |
| 4 Tebibits | 0.000000476837158203 Eio |
| 5 Tebibits | 0.000000596046447754 Eio |
| 10 Tebibits | 0.00000119209289551 Eio |
| 20 Tebibits | 0.00000238418579102 Eio |
| 25 Tebibits | 0.00000298023223877 Eio |
| 50 Tebibits | 0.00000596046447754 Eio |
| 100 Tebibits | 0.0000119209289551 Eio |
| Reference | Tebibits (Tibit) | Exbioctets (Eio) |
|---|---|---|
| A plain text message (160 characters) | 0.00000000116415 Tibit | 1.38778 × 10-16 Eio |
| A three-minute MP3 | 0.0000218279 Tibit | 2.60209 × 10-12 Eio |
| A smartphone photo | 0.0000291038 Tibit | 3.46945 × 10-12 Eio |
| A high-definition film | 0.0291038 Tibit | 0.00000000346945 Eio |
| A dual-layer Blu-ray disc | 0.363798 Tibit | 0.0000000433681 Eio |
The tebibit is a unit of digital information equal to 1,099,511,627,776 bits, which is 1,024 gibibits or two to the fortieth power. Its symbol is Tibit. It is the binary counterpart of the terabit, and the two now differ by 10 per cent, the point at which the distinction stops being pedantic and starts being financial.
That ten per cent is the reason the IEC prefixes exist. At the kibibit the discrepancy was 2.4 per cent and could be waved away; here it is a tenth of the quantity. In a contract for storage hardware, in a service agreement that guarantees capacity, or in a specification that a supplier must meet, a tenth is the difference between compliance and breach.
The unit's real home is flash memory, where dies are now made with capacities of one tebibit and above by stacking cell layers vertically. A modern flash die may hold a tebibit or two, and a package containing eight of them holds a teraoctet of raw capacity, from which spare blocks and management overhead are subtracted before anything reaches the user.
A tebibit is 137,438,953,472 octets, or 128 gibioctets. In practical terms it is the storage of a mid-range phone, or a couple of hours of uncompressed high-resolution video. The unit describes the raw material of storage devices rather than anything a person handles directly.
Filesystems also count in binary at this scale. A volume reported as 16 tebibytes by one tool and 17.6 terabytes by another is the same volume, and the difference is entirely in the base of the arithmetic. Anyone administering storage learns to check which convention a tool uses before comparing two numbers from different sources.
Correct notation is Tibit, with the capital T and lowercase i. It appears in flash memory datasheets, in filesystem documentation and in standards, and almost nowhere else. The presence of that lowercase i is the only reliable signal that a figure is binary, which is why careful technical writing uses it even when the difference seems small.
One tebibit equals 1,099,511,627,776 bits, 1,024 gibibits, 137,438,953,472 octets, or about 1.100 terabits.
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.