| Yottaoctets (Yo) | Mebioctets (Mio) |
|---|---|
| 1 Yottaoctet | 9.53674316406 × 1017 Mio |
| 2 Yottaoctets | 1.90734863281 × 1018 Mio |
| 3 Yottaoctets | 2.86102294922 × 1018 Mio |
| 4 Yottaoctets | 3.81469726562 × 1018 Mio |
| 5 Yottaoctets | 4.76837158203 × 1018 Mio |
| 10 Yottaoctets | 9.53674316406 × 1018 Mio |
| 20 Yottaoctets | 1.90734863281 × 1019 Mio |
| 25 Yottaoctets | 2.38418579102 × 1019 Mio |
| 50 Yottaoctets | 4.76837158203 × 1019 Mio |
| 100 Yottaoctets | 9.53674316406 × 1019 Mio |
| Reference | Yottaoctets (Yo) | Mebioctets (Mio) |
|---|---|---|
| A plain text message (160 characters) | 1.6 × 10-22 Yo | 0.000152588 Mio |
| A three-minute MP3 | 3 × 10-18 Yo | 2.86102 Mio |
| A smartphone photo | 4 × 10-18 Yo | 3.8147 Mio |
| A high-definition film | 4 × 10-15 Yo | 3814.7 Mio |
| A dual-layer Blu-ray disc | 5 × 10-14 Yo | 47683.7 Mio |
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.
The mebioctet is a unit of digital information equal to 1,048,576 octets, which is 1,024 kibioctets. Its symbol is Mio. It is the binary counterpart of the megaoctet, and the two differ by 4.9 per cent — the point at which a careful writer starts distinguishing them.
The unit's most visible home is the processor cache. The fast memory built into a processor to hold recently used data is sized in binary, and modern chips carry caches measured in mebioctets: a few hundred kibioctets at the second level and tens of mebioctets at the third. Those figures are exact powers of two because the cache is addressed by dividing an address into fixed bit fields.
Block sizes and buffers follow the same logic. Filesystems allocate in blocks, database engines read in pages, compression tools work in windows, and all of these are powers of two, most often a few mebioctets. A tool that offers a buffer of 16 megaoctets almost always means 16 mebioctets, because the underlying allocation is a shift rather than a multiplication.
The distinction has become visible to ordinary users through the discrepancy between what a download claims and what a file manager reports. A file described as 100 megaoctets on a website is often 100 mebioctets on disc, or the reverse, and the resulting 4.9 per cent difference is enough to make a progress bar look wrong without anything actually being wrong.
For scale, a mebioctet holds a million characters of unaccented text — roughly a long novel, or five hundred pages. It is also a single photograph from a modest camera, or eight seconds of high-definition video. The same unit therefore describes both a very large amount of text and a very small amount of video, which says a good deal about the relative cost of representing the two.
The IEC notation Mio is used in technical documentation, in the Linux kernel, in filesystem tools and in standards. It remains rare in consumer software, where MB is written for both quantities. When a figure matters, the safest habit is to compute in octets and convert once at the end.
One mebioctet equals 1,048,576 octets, 1,024 kibioctets, 8 mebibits, or about 1.049 megaoctets.