| Exbioctets (Eio) | Terabits (Tbit) |
|---|---|
| 1 Exbioctet | 9223372.03685 Tbit |
| 2 Exbioctets | 18446744.0737 Tbit |
| 3 Exbioctets | 27670116.1106 Tbit |
| 4 Exbioctets | 36893488.1474 Tbit |
| 5 Exbioctets | 46116860.1843 Tbit |
| 10 Exbioctets | 92233720.3685 Tbit |
| 20 Exbioctets | 184467440.737 Tbit |
| 25 Exbioctets | 230584300.921 Tbit |
| 50 Exbioctets | 461168601.843 Tbit |
| 100 Exbioctets | 922337203.685 Tbit |
| Reference | Exbioctets (Eio) | Terabits (Tbit) |
|---|---|---|
| A plain text message (160 characters) | 1.38778 × 10-16 Eio | 0.00000000128 Tbit |
| A three-minute MP3 | 2.60209 × 10-12 Eio | 0.000024 Tbit |
| A smartphone photo | 3.46945 × 10-12 Eio | 0.000032 Tbit |
| A high-definition film | 0.00000000346945 Eio | 0.032 Tbit |
| A dual-layer Blu-ray disc | 0.0000000433681 Eio | 0.4 Tbit |
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 terabit is a unit of digital information equal to one million million bits, a thousand gigabits. Its symbol is Tbit. It is the scale at which the internet's own infrastructure is measured — not the connection into a house, but the links between cities and across oceans.
A terabit is 125 gigaoctets. Put another way, one terabit is roughly the amount of data in a hundred and twenty-five hours of high-definition video, or the contents of a large laptop's disc. A single terabit-per-second link therefore moves the equivalent of that laptop every second, continuously.
Submarine cables are where these numbers live. A modern transoceanic cable carries several hundred terabits per second across a handful of fibre pairs, using wavelength division multiplexing to run dozens of separate light channels down the same glass strand at once. The cables laid across the Atlantic in the 2020s reach into the hundreds of terabits, where the first transatlantic telephone cable of 1956 carried thirty-six voice calls.
Internet exchange points, where networks meet and hand traffic to one another, publish their throughput in terabits per second. The largest in Europe and Asia peak in the tens of terabits, and those figures are among the most reliable public measurements of how much the internet is actually being used at a given moment.
Laboratory records go far higher. Research teams have pushed single optical fibres past a petabit per second by using multi-core fibre and hundreds of wavelengths simultaneously, though such experiments run over short distances under controlled conditions. The gap between what is demonstrated in a laboratory and what is deployed in the sea is usually about a decade.
For storage the terabit is used mainly in the semiconductor industry, where the density of a memory die is quoted in terabits per square centimetre or per package. Consumer products are labelled in octets instead — a terabit is 125 gigaoctets, so a chip described as 8 terabits appears on the shelf as a one-teraoctet drive.
One terabit equals 1,000,000,000,000 bits, 1,000 gigabits, 125 gigaoctets, or about 0.9095 tebibits.