| Bits per second (bit/s) | Gibioctets per second (Gio/s) |
|---|---|
| 1 Bit per second | 1.16415321827 × 10-10 Gio/s |
| 2 Bits per second | 2.32830643654 × 10-10 Gio/s |
| 3 Bits per second | 3.49245965481 × 10-10 Gio/s |
| 4 Bits per second | 4.65661287308 × 10-10 Gio/s |
| 5 Bits per second | 5.82076609135 × 10-10 Gio/s |
| 10 Bits per second | 0.00000000116415321827 Gio/s |
| 20 Bits per second | 0.00000000232830643654 Gio/s |
| 25 Bits per second | 0.00000000291038304567 Gio/s |
| 50 Bits per second | 0.00000000582076609135 Gio/s |
| 100 Bits per second | 0.0000000116415321827 Gio/s |
| Reference | Bits per second (bit/s) | Gibioctets per second (Gio/s) |
|---|---|---|
| A dial-up modem | 56000 bit/s | 0.00000651926 Gio/s |
| Typical home broadband | 100000000 bit/s | 0.0116415 Gio/s |
| Gigabit Ethernet | 1 × 109 bit/s | 0.116415 Gio/s |
| Streaming a 4K film | 25000000 bit/s | 0.00291038 Gio/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 gibioctet per second is a unit of data transfer rate equal to 1,073,741,824 octets per second, which is 1,024 mebioctets per second. Its symbol is Gio/s. It is the unit of memory bandwidth and of the fastest storage interfaces, and the binary counterpart of the gigaoctet per second, from which it differs by 7.4 per cent.
Memory is where the unit belongs most naturally. A memory channel transfers a fixed number of octets per clock cycle, and that number is a power of two, so the resulting bandwidth is a binary multiple of the clock frequency. A machine with several channels reaches tens of gibioctets per second, and an accelerator with stacked memory reaches thousands.
Storage has caught up. A fast solid-state drive on the current interface sustains several gibioctets per second, which means that for the first time the drive and the memory are within an order of magnitude of each other. That convergence has changed how software is written: the old assumption that reading from disc is thousands of times slower than reading from memory no longer holds.
The unit appears in benchmark output, in system monitoring displays and in the specifications of processor interconnects. All of these count in binary because the structures they measure are binary, and reporting the result with a decimal prefix would introduce a seven per cent error for the sake of a familiar-looking label.
For a sense of what the rate means, one gibioctet per second copies a two-gigaoctet film in under two seconds and fills a one-teraoctet drive in about a quarter of an hour. Anything at this speed is faster than every external connection in an ordinary building, so the limiting factor moves inside the machine.
The distinction from the decimal unit matters most in procurement and capacity planning. A specification that requires 10 gigaoctets per second and a system that delivers 10 gibioctets per second are not the same, and the difference of 7.4 per cent is the sort of margin that decides whether a design meets its requirement.
One gibioctet per second equals 1,073,741,824 octets per second, 1,024 mebioctets per second, or about 1.074 gigaoctets per second.