| Exaoctets per second (Eo/s) | Bits per second (bit/s) |
|---|---|
| 1 Exaoctet per second | 8 × 1018 bit/s |
| 2 Exaoctets per second | 1.6 × 1019 bit/s |
| 3 Exaoctets per second | 2.4 × 1019 bit/s |
| 4 Exaoctets per second | 3.2 × 1019 bit/s |
| 5 Exaoctets per second | 4 × 1019 bit/s |
| 10 Exaoctets per second | 8 × 1019 bit/s |
| 20 Exaoctets per second | 1.6 × 1020 bit/s |
| 25 Exaoctets per second | 2 × 1020 bit/s |
| 50 Exaoctets per second | 4 × 1020 bit/s |
| 100 Exaoctets per second | 8 × 1020 bit/s |
| Reference | Exaoctets per second (Eo/s) | Bits per second (bit/s) |
|---|---|---|
| A dial-up modem | 7 × 10-15 Eo/s | 56000 bit/s |
| Typical home broadband | 1.25 × 10-11 Eo/s | 100000000 bit/s |
| Gigabit Ethernet | 1.25 × 10-10 Eo/s | 1 × 109 bit/s |
| Streaming a 4K film | 3.125 × 10-12 Eo/s | 25000000 bit/s |
The exaoctet per second is a unit of data transfer rate equal to a thousand petaoctets per second, or eight exabits per second. Its symbol is Eo/s. Nothing built runs at this rate: it is about eight times the total traffic of the entire internet, counted across every network on the planet at once.
The unit is useful mainly for thought experiments about limits. If every hard drive and flash chip manufactured in a year were read simultaneously at full speed, the combined rate would be in this range. So would the total output of every camera sensor in every phone on Earth if they all recorded at once. These are sums over the whole world's hardware, not rates any system experiences.
There is one situation in which very large data volumes really do move faster than any network, and it puts the unit in perspective. Physically shipping a container of hard drives across an ocean transfers more data per second, averaged over the journey, than any cable. A shipping container holding a few exaoctets crossing the Atlantic in a week works out to several gigaoctets per second, and a truck of drives driven across a city beats almost any local link.
That calculation is not a joke; cloud providers offer it as a service. When a customer needs to move petaoctets into a data centre, the provider ships a lorry full of storage rather than attempting the transfer over a network, because the network would take months. The bandwidth of a vehicle is enormous, though its latency is measured in days.
For the unit itself, an exaoctet per second is 125 petaoctets per second, and it would transfer the world's entire stock of stored data — a few hundred zettaoctets — in about a week of continuous running. No mechanism exists to feed such a link, and none is being designed.
A converter must nevertheless handle the unit, because it appears in aggregate capacity models, in academic papers on the theoretical limits of communication, and in any table that lists the metric prefixes completely. A quantity does not need a use for its name to be well formed.
One exaoctet per second equals 1,000 petaoctets per second, 8 exabits per second, or about 0.8674 exbioctets 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.