| Kilobits per second (kbit/s) | Zebioctets per second (Zio/s) |
|---|---|
| 1 Kilobit per second | 1.05879118407 × 10-19 Zio/s |
| 2 Kilobits per second | 2.11758236814 × 10-19 Zio/s |
| 3 Kilobits per second | 3.1763735522 × 10-19 Zio/s |
| 4 Kilobits per second | 4.23516473627 × 10-19 Zio/s |
| 5 Kilobits per second | 5.29395592034 × 10-19 Zio/s |
| 10 Kilobits per second | 1.05879118407 × 10-18 Zio/s |
| 20 Kilobits per second | 2.11758236814 × 10-18 Zio/s |
| 25 Kilobits per second | 2.64697796017 × 10-18 Zio/s |
| 50 Kilobits per second | 5.29395592034 × 10-18 Zio/s |
| 100 Kilobits per second | 1.05879118407 × 10-17 Zio/s |
| Reference | Kilobits per second (kbit/s) | Zebioctets per second (Zio/s) |
|---|---|---|
| A dial-up modem | 56 kbit/s | 5.92923 × 10-18 Zio/s |
| Typical home broadband | 100000 kbit/s | 1.05879 × 10-14 Zio/s |
| Gigabit Ethernet | 1000000 kbit/s | 1.05879 × 10-13 Zio/s |
| Streaming a 4K film | 25000 kbit/s | 2.64698 × 10-15 Zio/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 zebioctet per second is a unit of data transfer rate equal to 1,024 exbioctets per second, or two to the seventieth power octets per second. Its symbol is Zio/s. It is the binary counterpart of the zettaoctet per second, and the two differ by 18.1 per cent.
A link running at this rate would transfer everything humanity has ever stored several times over in a single second. That is the plainest way to describe how far it lies beyond anything that exists, is planned, or has been seriously proposed. The unit is a name for a quantity, not a description of a thing.
It is worth being precise about why such names are still defined. A measurement system is a set of rules, and the value of a rule is that it applies without exception. The moment a system says that certain prefix-and-unit combinations are legal and others are not, every user must carry a table instead of a rule, and different users will carry different tables. Complete definition is cheaper and safer.
The physical obstacles are not merely large but qualitative. At a zebioctet per second, the energy needed to switch the required number of states, even at the thermodynamic minimum, becomes a substantial power; the practical figure for real electronics is many orders of magnitude above that; and the number of parallel channels required exceeds anything that could be built and cooled. These are not engineering targets.
The 18.1 per cent gap from the decimal unit continues the pattern that runs through the whole binary series. Each step multiplies the discrepancy by 1.024, so a convention that was harmless at the kibioctet has become, by this point, a difference no reader could overlook. Making that visible is the purpose the IEC prefixes serve.
In practice, a converter meets this unit only in a complete table or in a document exploring theoretical limits. Handling it correctly costs nothing and demonstrates that the tool applies its rules uniformly, which is the property that makes its ordinary answers trustworthy.
One zebioctet per second equals 1,024 exbioctets per second, 1,180,591,620,717,411,303,424 octets per second, or about 1.181 zettaoctets per second.