| Yobioctets per second (Yio/s) | Bits per second (bit/s) |
|---|---|
| 1 Yobioctet per second | 9.67140655692 × 1024 bit/s |
| 2 Yobioctets per second | 1.93428131138 × 1025 bit/s |
| 3 Yobioctets per second | 2.90142196708 × 1025 bit/s |
| 4 Yobioctets per second | 3.86856262277 × 1025 bit/s |
| 5 Yobioctets per second | 4.83570327846 × 1025 bit/s |
| 10 Yobioctets per second | 9.67140655692 × 1025 bit/s |
| 20 Yobioctets per second | 1.93428131138 × 1026 bit/s |
| 25 Yobioctets per second | 2.41785163923 × 1026 bit/s |
| 50 Yobioctets per second | 4.83570327846 × 1026 bit/s |
| 100 Yobioctets per second | 9.67140655692 × 1026 bit/s |
| Reference | Yobioctets per second (Yio/s) | Bits per second (bit/s) |
|---|---|---|
| A dial-up modem | 5.79026 × 10-21 Yio/s | 56000 bit/s |
| Typical home broadband | 1.03398 × 10-17 Yio/s | 100000000 bit/s |
| Gigabit Ethernet | 1.03398 × 10-16 Yio/s | 1 × 109 bit/s |
| Streaming a 4K film | 2.58494 × 10-18 Yio/s | 25000000 bit/s |
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.
The bit per second is the fundamental unit of data transfer rate. Its symbol is bit/s, often written bps. It counts how many binary decisions a channel carries in one second, and every other unit of transmission speed is a multiple of it.
Because it is a rate, it has the form of a quantity divided by time, exactly like metres per second or litres per second. That makes the arithmetic straightforward: a link running at a given number of bits per second, multiplied by a duration in seconds, gives the total number of bits transferred, and dividing by eight converts that to octets.
The unit must be distinguished from the baud, which counts symbols per second rather than bits. Early modems transmitted one bit per symbol, so the two numbers were the same and the words were used interchangeably. Modern schemes encode several bits in each symbol — by varying phase and amplitude together — so a channel running at 3,000 baud may carry 33,600 bits per second. Only the bit rate describes how much information moves.
Claude Shannon established the theoretical ceiling in 1948. The capacity of a channel in bits per second depends on its bandwidth and on the ratio of signal to noise, and no coding scheme can exceed it. Every advance in modem and radio design since has been an attempt to approach that limit more closely, and modern systems come within a fraction of a decibel of it.
In practice the raw bit rate of a link is never the rate at which useful data arrives. Protocol headers, error-correcting codes, acknowledgements and retransmissions all consume capacity, and the usable fraction is typically 90 to 95 per cent on a wired link and considerably less on a shared wireless one.
Single bits per second are rarely quoted, because almost every channel is faster. The exceptions are deep-space communication, where a probe billions of kilometres away may return data at a few tens of bits per second, and certain low-power sensor networks that transmit a handful of bits at long intervals to preserve battery life.
One bit per second equals 0.125 octets per second, 0.001 kilobits per second, or about 0.0009766 kibibits per second.