| Octets per second (octet/s) | Exbioctets per second (Eio/s) |
|---|---|
| 1 Octet per second | 8.67361737988 × 10-19 Eio/s |
| 2 Octets per second | 1.73472347598 × 10-18 Eio/s |
| 3 Octets per second | 2.60208521397 × 10-18 Eio/s |
| 4 Octets per second | 3.46944695195 × 10-18 Eio/s |
| 5 Octets per second | 4.33680868994 × 10-18 Eio/s |
| 10 Octets per second | 8.67361737988 × 10-18 Eio/s |
| 20 Octets per second | 1.73472347598 × 10-17 Eio/s |
| 25 Octets per second | 2.16840434497 × 10-17 Eio/s |
| 50 Octets per second | 4.33680868994 × 10-17 Eio/s |
| 100 Octets per second | 8.67361737988 × 10-17 Eio/s |
| Reference | Octets per second (octet/s) | Exbioctets per second (Eio/s) |
|---|---|---|
| A dial-up modem | 7000 octet/s | 6.07153 × 10-15 Eio/s |
| Typical home broadband | 12500000 octet/s | 1.0842 × 10-11 Eio/s |
| Gigabit Ethernet | 125000000 octet/s | 1.0842 × 10-10 Eio/s |
| Streaming a 4K film | 3125000 octet/s | 2.71051 × 10-12 Eio/s |
The octet per second is a unit of data transfer rate equal to eight bits per second. Its symbol is octet/s. It is the unit in which software reports transfer speeds, as against the bits per second in which hardware and network services advertise them, and the factor of eight between the two conventions is the source of endless confusion.
The division of labour is consistent once it is understood. Anything describing a physical link — an Ethernet port, a fibre connection, a radio channel, a broadband package — is quoted in bits per second, because bits are what the signalling actually carries. Anything describing a file moving from one place to another is quoted in octets per second, because files are measured in octets.
A download manager that reports 12 megaoctets per second on a connection sold as 100 megabits per second is not disagreeing with the advertisement; it is stating the same rate in the other convention, and the arithmetic between them is a division by eight. Recognising this immediately removes the most common cause of complaint about internet speed.
Individual octets per second appear in the same narrow places as individual bits: deep-space telemetry, low-power sensor links, and the slowest legacy serial connections. A rate of a hundred octets per second would move a page of text in about twenty seconds, which was a normal experience in the 1970s and is unimaginable now.
The unit also underlies the way disc and interface throughput is described. A drive that sustains 500 megaoctets per second is moving four gigabits per second across its interface, and matching the two figures is a routine part of system design: an interface rated in gigabits must be compared with a drive rated in octets, and the factor of eight decides whether one starves the other.
Storage tools reinforce the convention. Every file copy utility, backup program and command-line transfer tool reports in octets per second or its multiples, and every network measurement tool reports in bits per second. A person reading both at once has to keep the conversion in mind, which is exactly what makes the distinction worth stating explicitly.
One octet per second equals 8 bits per second, 0.008 kilobits per second, or 0.001 kilooctets per second.
The exbioctet per second is a unit of data transfer rate equal to 1,024 pebioctets per second, or two to the sixtieth power octets per second. Its symbol is Eio/s. It is the binary counterpart of the exaoctet per second, and the two differ by 15.3 per cent.
No machine, network or aggregate reaches this rate. An exbioctet per second is more than eight times the total instantaneous traffic of the entire internet, and it would move the world's whole stock of stored data in a matter of minutes. The unit describes a capacity with no source that could supply it and no destination that could take it in.
Two to the sixtieth is nevertheless a familiar number in computing, because it is the size of the address space a 64-bit machine can reach in octets divided by sixteen. The same power of two turns up in filesystem limits, in memory maps and in the design of every system built on that architecture, so the quantity is well known even though no rate approaches it.
The unit exists because the IEC series was defined completely. Every binary prefix pairs with every unit, exactly as every metric prefix does, so that a reader who has never seen Eio/s can decode it from the prefix alone. A system with gaps would need a table of permitted combinations, which is precisely what a rule-based system exists to avoid.
The difference from the decimal unit is worth restating at each level because it compounds. At the kibioctet it was 2.4 per cent, here it is more than an eighth, and at the yobioctet it will be more than a fifth. That growth is the reason the binary prefixes were created, and it is why the lowercase i has to be written even in figures nobody will check.
For a converter, the treatment is mechanical: six multiplications by 1,024 from octets, or the equivalent divisions coming down. The value of doing it correctly is not that anyone will use the result, but that a tool which handles every case the same way can be trusted on the cases that matter.
One exbioctet per second equals 1,024 pebioctets per second, 1,152,921,504,606,846,976 octets per second, or about 1.153 exaoctets per second.