| Yobioctets per second (Yio/s) | Mebioctets per second (Mio/s) |
|---|---|
| 1 Yobioctet per second | 1.15292150461 × 1018 Mio/s |
| 2 Yobioctets per second | 2.30584300921 × 1018 Mio/s |
| 3 Yobioctets per second | 3.45876451382 × 1018 Mio/s |
| 4 Yobioctets per second | 4.61168601843 × 1018 Mio/s |
| 5 Yobioctets per second | 5.76460752303 × 1018 Mio/s |
| 10 Yobioctets per second | 1.15292150461 × 1019 Mio/s |
| 20 Yobioctets per second | 2.30584300921 × 1019 Mio/s |
| 25 Yobioctets per second | 2.88230376152 × 1019 Mio/s |
| 50 Yobioctets per second | 5.76460752303 × 1019 Mio/s |
| 100 Yobioctets per second | 1.15292150461 × 1020 Mio/s |
| Reference | Yobioctets per second (Yio/s) | Mebioctets per second (Mio/s) |
|---|---|---|
| A dial-up modem | 5.79026 × 10-21 Yio/s | 0.00667572 Mio/s |
| Typical home broadband | 1.03398 × 10-17 Yio/s | 11.9209 Mio/s |
| Gigabit Ethernet | 1.03398 × 10-16 Yio/s | 119.209 Mio/s |
| Streaming a 4K film | 2.58494 × 10-18 Yio/s | 2.98023 Mio/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 mebioctet per second is a unit of data transfer rate equal to 1,048,576 octets per second, which is 1,024 kibioctets per second. Its symbol is Mio/s. It is the unit that disc benchmarks, copy tools and backup programs report in, and one of the few binary units most people see regularly without noticing.
Storage measurement produces it naturally. A benchmark writes and reads blocks whose size is a power of two, times the operation, and divides. The result is a binary rate, and reporting it as such preserves the arithmetic. A tool that converted to decimal megaoctets would introduce a 4.9 per cent adjustment for no purpose other than to match a marketing convention.
That five per cent is exactly where the two conventions diverge visibly for consumers. A drive advertised at 550 megaoctets per second and measured at 524 mebioctets per second is performing precisely as claimed; the numbers differ only because one is decimal and the other binary. A great deal of complaint about storage performance is this arithmetic misread as a shortfall.
For everyday sizes, one mebioctet per second copies a photograph in three seconds and a two-gigaoctet film in about half an hour. Modern drives run hundreds or thousands of times faster, so the unit is now the resolution at which small differences are reported rather than the scale of the whole figure.
The unit also appears in memory and cache measurements, in database throughput reports and in the output of the low-level commands that write disc images. All of these count in binary blocks because the underlying structures are binary, and all of them report in mebioctets per second because that is what the count divided by the time actually gives.
The habit of writing the lowercase i is worth keeping. It costs one character and it tells a later reader which of two conventions produced the number, which is information that cannot be recovered from context once it has been left out.
One mebioctet per second equals 1,048,576 octets per second, 1,024 kibioctets per second, or about 1.049 megaoctets per second.