| Kibibits per second (Kibit/s) | Zebibits per second (Zibit/s) |
|---|---|
| 1 Kibibit per second | 8.67361737988 × 10-19 Zibit/s |
| 2 Kibibits per second | 1.73472347598 × 10-18 Zibit/s |
| 3 Kibibits per second | 2.60208521397 × 10-18 Zibit/s |
| 4 Kibibits per second | 3.46944695195 × 10-18 Zibit/s |
| 5 Kibibits per second | 4.33680868994 × 10-18 Zibit/s |
| 10 Kibibits per second | 8.67361737988 × 10-18 Zibit/s |
| 20 Kibibits per second | 1.73472347598 × 10-17 Zibit/s |
| 25 Kibibits per second | 2.16840434497 × 10-17 Zibit/s |
| 50 Kibibits per second | 4.33680868994 × 10-17 Zibit/s |
| 100 Kibibits per second | 8.67361737988 × 10-17 Zibit/s |
| Reference | Kibibits per second (Kibit/s) | Zebibits per second (Zibit/s) |
|---|---|---|
| A dial-up modem | 54.6875 Kibit/s | 4.74338 × 10-17 Zibit/s |
| Typical home broadband | 97656.2 Kibit/s | 8.47033 × 10-14 Zibit/s |
| Gigabit Ethernet | 976562 Kibit/s | 8.47033 × 10-13 Zibit/s |
| Streaming a 4K film | 24414.1 Kibit/s | 2.11758 × 10-14 Zibit/s |
The kibibit per second is a unit of data transfer rate equal to 1,024 bits per second. Its symbol is Kibit/s. It is the binary counterpart of the kilobit per second, and it is the least used member of an already unusual family, because transfer rates are one of the few places in computing where the decimal convention has always been unambiguous.
Networking has counted in true thousands from the beginning. A modem rated at 56 kilobits per second meant fifty-six thousand, not fifty-seven thousand three hundred and forty-four. The reason is that a transmission rate is set by a clock, and clocks are specified in decimal frequencies: a link running at ten million symbols per second carries a decimal number of bits, not a power of two.
The binary prefixes exist for quantities, not for rates, because quantities of storage are organised in powers of two while time is not. There is no natural reason for a rate to be a power of two, and consequently no reason for a rate unit to need a binary prefix. Where one appears, it is almost always because a program divided a binary file size by a duration.
That is exactly where the kibibit per second does turn up. A tool that measures a transfer by counting kibioctets and dividing by seconds produces a rate in kibioctets per second, and multiplying by eight gives kibibits per second. The unit is a consequence of the arithmetic rather than a description of the channel.
For scale, a kibibit per second is 128 octets per second, and the difference from a kilobit per second is 2.4 per cent — smaller than the measurement error of almost any real throughput test. At this level the distinction is technically correct and practically invisible, which is a fair description of the whole binary prefix system at its lower end.
The unit is properly defined and a converter must handle it, because the IEC series applies to every unit without exception. Whether anyone writes it is a separate question from whether it means something definite, and it does.
One kibibit per second equals 1,024 bits per second, 128 octets per second, or 1.024 kilobits per second.
The zebibit per second is a unit of data transfer rate equal to two to the seventieth power bits per second, which is 1,024 exbibits per second. Its symbol is Zibit/s. It is the binary counterpart of the zettabit per second, and the two differ by 18.1 per cent — approaching a fifth.
Nothing runs at this rate, and nothing is designed to. A zebibit per second is about a thousand times the total instantaneous traffic of the internet, and it would move the world's entire stock of stored data in a matter of minutes. The unit exists because the IEC series, like the metric series it parallels, was defined completely rather than only as far as anyone then needed.
That completeness is a deliberate design principle rather than an oversight. A measurement system whose names run out at some arbitrary point forces every future user to improvise an extension, and improvised extensions conflict with one another. Defining the whole ladder in advance costs nothing and removes the possibility.
The eighteen per cent gap at this level is the clearest illustration of why the binary series was needed at all. At the kibibit the two conventions differed by 2.4 per cent, which nobody noticed; the discrepancy multiplies by 1.024 at each step, and by here it is large enough that no reader could treat the two labels as interchangeable even in casual writing.
In octets a zebibit per second is 147,573,952,589,676,412,928, or 128 exbioctets per second. Expressing the same rate in every unit on the scale is an exercise rather than an application, but it is one a converter has to perform correctly, because the arithmetic does not become approximate when the quantity becomes unreachable.
The practical lesson is the one the whole binary series teaches: the lowercase i is not optional. It is the only mark in a written figure that distinguishes a power of two from a power of ten, and by this point in the scale the two are nearly a fifth apart.
One zebibit per second equals 1,024 exbibits per second, 147,573,952,589,676,412,928 octets per second, or about 1.181 zettabits per second.