| Kilooctets per second (ko/s) | Yobioctets per second (Yio/s) |
|---|---|
| 1 Kilooctet per second | 8.27180612553 × 10-22 Yio/s |
| 2 Kilooctets per second | 1.65436122511 × 10-21 Yio/s |
| 3 Kilooctets per second | 2.48154183766 × 10-21 Yio/s |
| 4 Kilooctets per second | 3.30872245021 × 10-21 Yio/s |
| 5 Kilooctets per second | 4.13590306277 × 10-21 Yio/s |
| 10 Kilooctets per second | 8.27180612553 × 10-21 Yio/s |
| 20 Kilooctets per second | 1.65436122511 × 10-20 Yio/s |
| 25 Kilooctets per second | 2.06795153138 × 10-20 Yio/s |
| 50 Kilooctets per second | 4.13590306277 × 10-20 Yio/s |
| 100 Kilooctets per second | 8.27180612553 × 10-20 Yio/s |
| Reference | Kilooctets per second (ko/s) | Yobioctets per second (Yio/s) |
|---|---|---|
| A dial-up modem | 7 ko/s | 5.79026 × 10-21 Yio/s |
| Typical home broadband | 12500 ko/s | 1.03398 × 10-17 Yio/s |
| Gigabit Ethernet | 125000 ko/s | 1.03398 × 10-16 Yio/s |
| Streaming a 4K film | 3125 ko/s | 2.58494 × 10-18 Yio/s |
The kilooctet per second is a unit of data transfer rate equal to one thousand octets per second, and therefore to eight kilobits per second. Its symbol is ko/s. It is the unit in which file transfers were reported through the whole of the dial-up era, and it still appears whenever a transfer is slow enough to need it.
The conversion from advertised connection speeds is the reason it matters. A 56-kilobit modem delivered about 7 kilooctets per second in practice, and users learned the relationship by watching progress bars: a one-megaoctet file took about two and a half minutes. The habit of dividing the advertised number by eight and then subtracting a bit for overhead dates from that period.
Storage devices of the era were similar. A floppy disc drive read at roughly 30 to 60 kilooctets per second, a single-speed compact-disc drive at 150, and an early hard drive at a few hundred. Loading a program from any of them was a matter of seconds to minutes, and software was written with that expectation in mind.
The unit still appears in serial communication. The classic serial port ran at rates up to 115,200 bits per second, which is 14.4 kilooctets per second, and equivalent rates are still used to talk to microcontrollers, scientific instruments and industrial equipment. A protocol designed for such a link cannot assume that a large message will arrive quickly.
It also appears at the bottom end of modern networking. A congested mobile connection, a distant satellite link or a heavily shared wireless network can fall to a few tens of kilooctets per second, and at that rate an ordinary web page — which now runs to a few megaoctets — takes a minute or more to load. The unit is a reminder of what the network assumes about its users.
For scale, one kilooctet per second moves a thousand characters of plain text each second, so a short letter transfers in a second and a novel in about ten minutes. Nothing about text has ever needed more than this; every increase in transfer rate since has been consumed by images, sound and video.
One kilooctet per second equals 1,000 octets per second, 8 kilobits per second, or about 0.9766 kibioctets 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.