| Bits per second (bit/s) | Zebioctets per second (Zio/s) |
|---|---|
| 1 Bit per second | 1.05879118407 × 10-22 Zio/s |
| 2 Bits per second | 2.11758236814 × 10-22 Zio/s |
| 3 Bits per second | 3.1763735522 × 10-22 Zio/s |
| 4 Bits per second | 4.23516473627 × 10-22 Zio/s |
| 5 Bits per second | 5.29395592034 × 10-22 Zio/s |
| 10 Bits per second | 1.05879118407 × 10-21 Zio/s |
| 20 Bits per second | 2.11758236814 × 10-21 Zio/s |
| 25 Bits per second | 2.64697796017 × 10-21 Zio/s |
| 50 Bits per second | 5.29395592034 × 10-21 Zio/s |
| 100 Bits per second | 1.05879118407 × 10-20 Zio/s |
| Reference | Bits per second (bit/s) | Zebioctets per second (Zio/s) |
|---|---|---|
| A dial-up modem | 56000 bit/s | 5.92923 × 10-18 Zio/s |
| Typical home broadband | 100000000 bit/s | 1.05879 × 10-14 Zio/s |
| Gigabit Ethernet | 1 × 109 bit/s | 1.05879 × 10-13 Zio/s |
| Streaming a 4K film | 25000000 bit/s | 2.64698 × 10-15 Zio/s |
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.
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.