| Zebibits per second (Zibit/s) | Kibioctets per second (Kio/s) |
|---|---|
| 1 Zebibit per second | 1.44115188076 × 1017 Kio/s |
| 2 Zebibits per second | 2.88230376152 × 1017 Kio/s |
| 3 Zebibits per second | 4.32345564228 × 1017 Kio/s |
| 4 Zebibits per second | 5.76460752303 × 1017 Kio/s |
| 5 Zebibits per second | 7.20575940379 × 1017 Kio/s |
| 10 Zebibits per second | 1.44115188076 × 1018 Kio/s |
| 20 Zebibits per second | 2.88230376152 × 1018 Kio/s |
| 25 Zebibits per second | 3.6028797019 × 1018 Kio/s |
| 50 Zebibits per second | 7.20575940379 × 1018 Kio/s |
| 100 Zebibits per second | 1.44115188076 × 1019 Kio/s |
| Reference | Zebibits per second (Zibit/s) | Kibioctets per second (Kio/s) |
|---|---|---|
| A dial-up modem | 4.74338 × 10-17 Zibit/s | 6.83594 Kio/s |
| Typical home broadband | 8.47033 × 10-14 Zibit/s | 12207 Kio/s |
| Gigabit Ethernet | 8.47033 × 10-13 Zibit/s | 122070 Kio/s |
| Streaming a 4K film | 2.11758 × 10-14 Zibit/s | 3051.76 Kio/s |
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.
The kibioctet per second is a unit of data transfer rate equal to 1,024 octets per second, and therefore to 8,192 bits per second. Its symbol is Kio/s. Unlike most of the binary rate units it is genuinely common, because the command-line tools that copy, download and synchronise files have reported in it for decades.
The reason is straightforward. Those tools count what they have moved in blocks, and blocks are powers of two. A program that reads in four-kibioctet pieces and divides the total by elapsed time produces a rate in kibioctets per second, and reporting it in decimal kilooctets would require an extra multiplication for no benefit. The unit is what the arithmetic naturally produces.
Anyone who has watched a file copy on a Unix-like system has seen the figure. Download utilities, archive tools, disc-writing commands and network file transfer programs all report progress in kibioctets or mebioctets per second, and most of them label it correctly with the lowercase i. It is one of the few places where the IEC prefixes are used consistently in everyday software.
For scale, a kibioctet per second moves about a thousand characters of text each second: a short letter in a second, a novel in about ten minutes. It is a rate at which a modern web page will not load in any reasonable time, so seeing it in a progress display usually means something has gone wrong with the connection rather than that the transfer is nearly finished.
The difference from a kilooctet per second is 2.4 per cent, which nobody notices. The value of using the binary unit here is not accuracy but honesty: the number came from a binary computation, and writing it with a binary prefix says so. A reader who wants the decimal figure can convert; a reader given a decimal label for a binary number cannot recover anything.
Comparing the reading with an advertised connection speed requires two steps: multiply by eight to get bits, and adjust by 2.4 per cent for the base. In practice the second step is beneath the noise of any real measurement, and the first is the one that matters.
One kibioctet per second equals 1,024 octets per second, 8,192 bits per second, or 1.024 kilooctets per second.