| Octets per second (octet/s) | Exbibits per second (Eibit/s) |
|---|---|
| 1 Octet per second | 6.93889390391 × 10-18 Eibit/s |
| 2 Octets per second | 1.38777878078 × 10-17 Eibit/s |
| 3 Octets per second | 2.08166817117 × 10-17 Eibit/s |
| 4 Octets per second | 2.77555756156 × 10-17 Eibit/s |
| 5 Octets per second | 3.46944695195 × 10-17 Eibit/s |
| 10 Octets per second | 6.93889390391 × 10-17 Eibit/s |
| 20 Octets per second | 1.38777878078 × 10-16 Eibit/s |
| 25 Octets per second | 1.73472347598 × 10-16 Eibit/s |
| 50 Octets per second | 3.46944695195 × 10-16 Eibit/s |
| 100 Octets per second | 6.93889390391 × 10-16 Eibit/s |
| Reference | Octets per second (octet/s) | Exbibits per second (Eibit/s) |
|---|---|---|
| A dial-up modem | 7000 octet/s | 4.85723 × 10-14 Eibit/s |
| Typical home broadband | 12500000 octet/s | 8.67362 × 10-11 Eibit/s |
| Gigabit Ethernet | 125000000 octet/s | 8.67362 × 10-10 Eibit/s |
| Streaming a 4K film | 3125000 octet/s | 2.1684 × 10-11 Eibit/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 exbibit per second is a unit of data transfer rate equal to two to the sixtieth power bits per second, which is 1,024 pebibits per second. Its symbol is Eibit/s. It is the binary counterpart of the exabit per second, and the two differ by 15.3 per cent.
That fifteen per cent is more than the margin most engineering work allows anywhere. A quantity stated in the wrong convention at this level is not slightly imprecise but plainly wrong, and no amount of context recovers the intended figure once it has been written ambiguously. This is the situation the IEC prefixes were introduced to prevent.
No physical link approaches this rate. The unit describes aggregates: the total instantaneous traffic of the whole internet is roughly an exabit per second, so a binary exbibit per second is fifteen per cent more than everything moving on every network on the planet at a given moment.
Where a binary figure of this size arises naturally is in address arithmetic rather than in transmission. Two to the sixtieth is a number that appears throughout the design of 64-bit systems, and any rate derived from filling or traversing such an address space in a fixed time is naturally binary. Those calculations are theoretical, but they are the reason the unit is defined rather than left unnamed.
In octets an exbibit per second is 144,115,188,075,855,872, or 128 pebioctets per second. That is more storage moved per second than the world manufactures in several years, which is a way of saying that no source and no destination for such a flow could exist.
For a converter the treatment is mechanical and must be exact. Eibit/s and Ebit/s differ by an eighth, and a tool that treats them as interchangeable has introduced an error larger than the difference between many neighbouring units. The lowercase i is not decoration.
One exbibit per second equals 1,024 pebibits per second, 144,115,188,075,855,872 octets per second, or about 1.153 exabits per second.