| Mebioctets (Mio) | Pebioctets (Pio) |
|---|---|
| 1 Mebioctet | 9.31322574615 × 10-10 Pio |
| 2 Mebioctets | 0.00000000186264514923 Pio |
| 3 Mebioctets | 0.00000000279396772385 Pio |
| 4 Mebioctets | 0.00000000372529029846 Pio |
| 5 Mebioctets | 0.00000000465661287308 Pio |
| 10 Mebioctets | 0.00000000931322574615 Pio |
| 20 Mebioctets | 0.0000000186264514923 Pio |
| 25 Mebioctets | 0.0000000232830643654 Pio |
| 50 Mebioctets | 0.0000000465661287308 Pio |
| 100 Mebioctets | 0.0000000931322574615 Pio |
| Reference | Mebioctets (Mio) | Pebioctets (Pio) |
|---|---|---|
| A plain text message (160 characters) | 0.000152588 Mio | 1.42109 × 10-13 Pio |
| A three-minute MP3 | 2.86102 Mio | 0.00000000266454 Pio |
| A smartphone photo | 3.8147 Mio | 0.00000000355271 Pio |
| A high-definition film | 3814.7 Mio | 0.00000355271 Pio |
| A dual-layer Blu-ray disc | 47683.7 Mio | 0.0000444089 Pio |
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.
The pebioctet is a unit of digital information equal to 1,125,899,906,842,624 octets, which is 1,024 tebioctets. Its symbol is Pio. It is the binary counterpart of the petaoctet, and the two now differ by 12.6 per cent.
This is the unit in which filesystem limits are written. Several widely deployed filesystems have maximum file or volume sizes that are exact powers of two, and those limits fall in this range: sixteen tebioctets for one, a pebioctet for another, eight pebioctets for a third. The numbers are not choices made by anyone; they follow from how many bits the filesystem uses to number its blocks.
Large scientific and commercial storage systems are also sized here. A research computing centre may run a filesystem of several pebioctets across thousands of drives, and the tools that manage it report in pebioctets because the underlying allocation is binary throughout. Converting those figures to decimal units for a report introduces an error of an eighth for no benefit.
A pebioctet is roughly a thousand large consumer hard drives, or the complete video output of a broadcaster over many years. It is also close to the size of the largest single scientific archives, though those are typically stated in petaoctets by press offices and in pebioctets by the engineers who run them, which produces two different numbers for the same building.
Distinguishing the two is not pedantry at this level. A twelve per cent difference on a purchase of many pebioctets is a large sum of money, and a capacity plan built on the wrong unit will be wrong by more than the margin most plans allow. This is precisely the situation the IEC prefixes were introduced to prevent.
The symbol Pio is used in filesystem documentation, in storage system manuals and in standards. Where a source writes PB without saying which it means, the difference is an eighth, and the honest thing for a reader to do is treat the figure as approximate rather than assume one convention or the other.
One pebioctet equals 1,024 tebioctets, 1,125,899,906,842,624 octets, 8 pebibits, or about 1.126 petaoctets.