| Kilobits per second (kbit/s) | Yobioctets per second (Yio/s) |
|---|---|
| 1 Kilobit per second | 1.03397576569 × 10-22 Yio/s |
| 2 Kilobits per second | 2.06795153138 × 10-22 Yio/s |
| 3 Kilobits per second | 3.10192729707 × 10-22 Yio/s |
| 4 Kilobits per second | 4.13590306277 × 10-22 Yio/s |
| 5 Kilobits per second | 5.16987882846 × 10-22 Yio/s |
| 10 Kilobits per second | 1.03397576569 × 10-21 Yio/s |
| 20 Kilobits per second | 2.06795153138 × 10-21 Yio/s |
| 25 Kilobits per second | 2.58493941423 × 10-21 Yio/s |
| 50 Kilobits per second | 5.16987882846 × 10-21 Yio/s |
| 100 Kilobits per second | 1.03397576569 × 10-20 Yio/s |
| Reference | Kilobits per second (kbit/s) | Yobioctets per second (Yio/s) |
|---|---|---|
| A dial-up modem | 56 kbit/s | 5.79026 × 10-21 Yio/s |
| Typical home broadband | 100000 kbit/s | 1.03398 × 10-17 Yio/s |
| Gigabit Ethernet | 1000000 kbit/s | 1.03398 × 10-16 Yio/s |
| Streaming a 4K film | 25000 kbit/s | 2.58494 × 10-18 Yio/s |
The kilobit per second is a unit of data transfer rate equal to one thousand bits per second. Its symbol is kbit/s, often written kbps. It was the unit of the dial-up era, and it survives today as the unit in which audio and speech encoding rates are quoted.
The dial-up sequence is worth recalling because each number marks a technical generation. Modems ran at 300 bits per second in the late 1970s, then 1,200, 2,400, 9,600, 14,400, 28,800, 33,600 and finally 56 kilobits per second at the end of the 1990s. That last figure was the ceiling of an ordinary telephone line, set by the eight-kilohertz sampling of the digital telephone network rather than by the modem.
Audio encoding is where the unit now lives. Telephone-quality speech runs at 8 to 64 kilobits per second depending on the codec, with modern low-rate codecs producing intelligible speech at 8 and high-quality voice calls at 24 to 32. Music at 128 kilobits per second was the early standard of portable players, 192 and 256 are common, and 320 is the practical ceiling of the older lossy formats.
Those numbers reward a moment of arithmetic. Music at 128 kilobits per second is 16 kilooctets per second, so a four-minute track is about 3.8 megaoctets. Uncompressed compact-disc audio runs at 1,411 kilobits per second, so the compressed file is about a tenth the size of the original, which is the whole point of the format.
Video subtitle streams, control channels and telemetry links also work in kilobits per second. So does much of the machine-to-machine traffic that fills modern networks: a sensor reporting a reading every few seconds needs a fraction of a kilobit per second, and the protocols designed for such devices are built around keeping the radio switched off most of the time.
The unit's lower-case k marks the decimal kilo, one thousand exactly. In transmission this has never been ambiguous, because network rates have always been counted in true thousands; the binary confusion that afflicts storage units does not arise here, and a kilobit per second means the same thing in every document.
One kilobit per second equals 1,000 bits per second, 125 octets per second, or about 0.9766 kibibits 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.