| Kibioctets per second (Kio/s) | Yobioctets per second (Yio/s) |
|---|---|
| 1 Kibioctet per second | 8.47032947254 × 10-22 Yio/s |
| 2 Kibioctets per second | 1.69406589451 × 10-21 Yio/s |
| 3 Kibioctets per second | 2.54109884176 × 10-21 Yio/s |
| 4 Kibioctets per second | 3.38813178902 × 10-21 Yio/s |
| 5 Kibioctets per second | 4.23516473627 × 10-21 Yio/s |
| 10 Kibioctets per second | 8.47032947254 × 10-21 Yio/s |
| 20 Kibioctets per second | 1.69406589451 × 10-20 Yio/s |
| 25 Kibioctets per second | 2.11758236814 × 10-20 Yio/s |
| 50 Kibioctets per second | 4.23516473627 × 10-20 Yio/s |
| 100 Kibioctets per second | 8.47032947254 × 10-20 Yio/s |
| Reference | Kibioctets per second (Kio/s) | Yobioctets per second (Yio/s) |
|---|---|---|
| A dial-up modem | 6.83594 Kio/s | 5.79026 × 10-21 Yio/s |
| Typical home broadband | 12207 Kio/s | 1.03398 × 10-17 Yio/s |
| Gigabit Ethernet | 122070 Kio/s | 1.03398 × 10-16 Yio/s |
| Streaming a 4K film | 3051.76 Kio/s | 2.58494 × 10-18 Yio/s |
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.
The yobioctet per second is a unit of data transfer rate equal to 1,024 zebioctets per second, or two to the eightieth power octets per second. Its symbol is Yio/s. It is the largest binary rate the International Electrotechnical Commission has named, and the last rung of the ladder that began with the bit per second.
At this final step the binary and decimal conventions differ by 20.9 per cent. That figure closes the argument the IEC prefixes were created to settle: a naming habit that was 2.4 per cent wrong at the kibibit per second has grown, through eight successive multiplications by 1.024, into a discrepancy of more than a fifth. No system of measurement can carry an ambiguity that large, and the whole binary series exists to remove it.
The rate itself has no referent. A yobioctet per second is more than eight million times the total instantaneous traffic of the internet, and it would transfer everything humanity has ever stored several thousand times over in a second. Nothing produces data at that rate, nothing consumes it, and nothing is designed with it in view.
That does not make the unit pointless. Defining the whole ladder in advance means that the rule — every prefix combines with every unit — is all anyone has to learn, and a rule is easier to carry than a table of exceptions. The same principle gave the metric system its complete prefix set, and the addition of ronna and quetta in 2022 extended the decimal side without any matching binary names being defined.
The practical value of a unit like this is that it makes a converter's behaviour uniform. A tool that handles the impossible cases by the same rule as the ordinary ones can be trusted not to have special cases hidden in it, and that is a property worth having in something whose whole purpose is to be relied upon.
For the reader, the whole series comes down to one character: Kio/s, Mio/s, Gio/s, Tio/s, Pio/s, Eio/s, Zio/s and Yio/s are binary; ko/s, Mo/s, Go/s, To/s, Po/s, Eo/s, Zo/s and Yo/s are decimal; and the difference between them widens from a rounding error to a fifth as you climb.
One yobioctet per second equals 1,024 zebioctets per second, 1,208,925,819,614,629,174,706,176 octets per second, or about 1.209 yottaoctets per second.