Conversion from Zettabits per second to Bits per second

Information about the Zettabit per second (Zbit/s)

The zettabit per second is a unit of data transfer rate equal to a thousand exabits per second. Its symbol is Zbit/s. No system on Earth moves data at this rate, and none is planned; the unit exists because the metric system defines every prefix for every unit, whether or not the combination has yet been needed.

To see how far off it is, take the whole internet. Global traffic at present runs at roughly one exabit per second on average, so the entire planet's communications would have to grow a thousandfold to reach one zettabit per second. At the growth rates of the last two decades that would take somewhere between twenty and thirty years, which is precisely the sort of extrapolation that has been wrong in both directions before.

A zettabit per second is 125 exaoctets per second. Since global data storage manufacturing runs at a few hundred exaoctets a year, a link at this rate would transfer the world's entire annual production of new storage capacity in a couple of seconds. Nothing could be stored at the far end; the data would have to be processed and discarded as it arrived.

That last point is not as fanciful as it sounds. Several existing systems already discard almost everything they receive: particle detectors, radio telescope arrays and network monitoring systems all process far more than they keep, because keeping it is impossible and unnecessary. A zettabit-per-second link would be an extreme case of an architecture that already exists.

The physical obstacles are less absolute than they might appear. The theoretical capacity of a single optical fibre is far above what is used today, and the practical limits come from amplifier noise, non-linear effects and the electronics at each end rather than from the glass itself. Aggregating enough fibres would reach a zettabit per second; the difficulty is that nobody has a reason to.

For a converter, the unit matters because forecasts and capacity models are written in whatever unit keeps the numbers legible. A projection that reaches into the 2050s may reasonably state totals in zettabits per second, and a reader needs to be able to convert that into something familiar.

One zettabit per second equals 1,000 exabits per second, 125 exaoctets per second, or about 0.8470 zebibits per second.

Information about the Bit per second (bit/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.