| Zebibits (Zibit) | Yottaoctets (Yo) |
|---|---|
| 1 Zebibit | 0.00014757395259 Yo |
| 2 Zebibits | 0.000295147905179 Yo |
| 3 Zebibits | 0.000442721857769 Yo |
| 4 Zebibits | 0.000590295810359 Yo |
| 5 Zebibits | 0.000737869762948 Yo |
| 10 Zebibits | 0.0014757395259 Yo |
| 20 Zebibits | 0.00295147905179 Yo |
| 25 Zebibits | 0.00368934881474 Yo |
| 50 Zebibits | 0.00737869762948 Yo |
| 100 Zebibits | 0.014757395259 Yo |
| Reference | Zebibits (Zibit) | Yottaoctets (Yo) |
|---|---|---|
| A plain text message (160 characters) | 1.0842 × 10-18 Zibit | 1.6 × 10-22 Yo |
| A three-minute MP3 | 2.03288 × 10-14 Zibit | 3 × 10-18 Yo |
| A smartphone photo | 2.71051 × 10-14 Zibit | 4 × 10-18 Yo |
| A high-definition film | 2.71051 × 10-11 Zibit | 4 × 10-15 Yo |
| A dual-layer Blu-ray disc | 3.38813 × 10-10 Zibit | 5 × 10-14 Yo |
The zebibit is a unit of digital information equal to two to the seventieth power bits, which is 1,024 exbibits. Its symbol is Zibit. It is the binary counterpart of the zettabit, and the two now differ by 18.1 per cent — nearly a fifth.
That divergence is the reason the binary prefixes were needed at all. At the kibibit the two conventions differed by 2.4 per cent, a rounding error. Here the difference is large enough that a document using the wrong one is simply reporting a different quantity, and no amount of context can repair the ambiguity after the fact.
A zebibit is 147,573,952,589,676,412,928 octets, or 128 exbioctets. Nothing of this size exists. The total data held by humanity is somewhere in the low hundreds of zettaoctets, which is under a zebioctet, so the world's entire information stock does not yet reach one unit at this step of the binary ladder.
The unit exists because the IEC series was defined completely rather than as far as anyone then needed. That is the same principle the metric system follows: every prefix applies to every unit, whether or not the combination has yet been used. A system with holes in it requires a table of exceptions, and a system without holes requires only the rule.
Where the zebibit could genuinely appear is in address space arithmetic. Two to the seventieth is not a natural pointer width, but multiples and fractions of powers of two run through every discussion of addressing, and a scheme that reserved seventy bits for something would naturally be described in these terms. Such schemes are proposed occasionally and none has yet been needed.
Reading the symbol is the practical skill. Zibit is binary, Zbit is decimal, and at eighteen per cent apart the two are not interchangeable in any document where the number matters. Where a source writes ZB with no explanation, there is no way to know which was meant, and the honest response is to treat the figure as uncertain to a fifth.
One zebibit equals 1,024 exbibits, 147,573,952,589,676,412,928 octets, or about 1.181 zettabits.
The yottaoctet is a unit of digital information equal to a thousand zettaoctets, or a septillion octets — a one followed by twenty-four zeros. Its symbol is Yo. Nothing that exists is measured in yottaoctets; the unit describes a quantity of data the world has not yet produced.
The total data held by humanity is currently estimated in the low hundreds of zettaoctets, so the world is a small fraction of the way to its first yottaoctet. On the growth rates of the last two decades, that threshold would be crossed sometime in the 2040s, though every long-range forecast in this field has been wrong in both directions.
The physical obstacles are severe. At the storage densities of current hard drives, a yottaoctet would need something like a hundred billion units. Manufacturing them at present rates would take centuries, powering them would need the electrical output of many countries, and housing them would require a building programme without precedent. The number is not absurd, but it is far beyond the current industrial base.
Research into higher-density storage exists partly because of this ceiling. DNA data storage, which encodes information in synthetic genetic sequences, offers densities millions of times higher than magnetic media, and a yottaoctet of DNA would fit in a room rather than a continent. Reading and writing it remain slow and costly, but the density argument is what keeps the field funded.
The yottaoctet also appears in claims that turn out to be exaggerated. Reports that intelligence agencies were building yottaoctet-scale facilities circulated widely in the 2010s and were not supported by the construction, the power supply or the storage market. Any claim about a yottaoctet of anything can be checked against total world manufacturing, which is a useful discipline.
Between 1991 and 2022 the yotta prefix was the top of the metric ladder, which is why it was the natural unit for speculative claims. The addition of ronna and quetta in 2022 gave the system three more decimal orders above it, and it is telling that this was done partly because data quantities were approaching the old ceiling.
One yottaoctet equals 1,000 zettaoctets, 1,000,000,000,000,000 gigaoctets, 8 yottabits, or about 0.8272 yobioctets.