| Tebioctets (Tio) | Octets (octet) |
|---|---|
| 1 Tebioctet | 1099511627776 octet |
| 2 Tebioctets | 2199023255552 octet |
| 3 Tebioctets | 3298534883328 octet |
| 4 Tebioctets | 4398046511104 octet |
| 5 Tebioctets | 5497558138880 octet |
| 10 Tebioctets | 10995116277760 octet |
| 20 Tebioctets | 21990232555520 octet |
| 25 Tebioctets | 27487790694400 octet |
| 50 Tebioctets | 54975581388800 octet |
| 100 Tebioctets | 109951162777600 octet |
| Reference | Tebioctets (Tio) | Octets (octet) |
|---|---|---|
| A plain text message (160 characters) | 1.45519 × 10-10 Tio | 160 octet |
| A three-minute MP3 | 0.00000272848 Tio | 3000000 octet |
| A smartphone photo | 0.00000363798 Tio | 4000000 octet |
| A high-definition film | 0.00363798 Tio | 4 × 109 octet |
| A dual-layer Blu-ray disc | 0.0454747 Tio | 5 × 1010 octet |
The tebioctet is a unit of digital information equal to 1,099,511,627,776 octets, which is 1,024 gibioctets. Its symbol is Tio. It is the binary counterpart of the teraoctet, and at this level the two differ by 10 per cent — the gap that produces the most familiar complaint in consumer computing.
That complaint runs as follows. A drive is sold as one teraoctet, holds exactly one million million octets, and the operating system reports 931 gigaoctets. What it is actually reporting is 0.909 tebioctets, expressed with the wrong label. Nothing is missing from the drive; the number has simply been divided by 1,024 three times and then written with a decimal prefix.
Storage administration lives in this unit. Volume sizes, RAID array capacities, snapshot reserves and quota limits are all quoted in tebioctets by the tools that manage them, because the underlying allocation units are powers of two. A filesystem asked to create a 10-teraoctet volume and one asked to create a 10-tebioctet volume will produce visibly different results.
The difference matters commercially as well as technically. Cloud storage priced per teraoctet and cloud storage priced per tebioctet differ by a tenth in the quantity delivered for the same price, and a contract that does not say which is being used is genuinely ambiguous. Careful procurement documents specify the unit explicitly for exactly this reason.
A tebioctet holds around a quarter of a million photographs, two hundred hours of high-definition video, or the complete text of every book in a large public library many times over. In a household it is more storage than a lifetime of ordinary files will use; in a video production company it is a few days of work.
The correct symbol Tio appears in filesystem tools, in storage array documentation and in standards, and it is worth using even when the audience is unlikely to notice. A figure written with a binary prefix can be converted correctly by anyone who reads it later; one written ambiguously cannot be repaired.
One tebioctet equals 1,099,511,627,776 octets, 1,024 gibioctets, 8 tebibits, or about 1.100 teraoctets.
The octet is a unit of digital information equal to exactly eight bits. Its symbol is octet, and its name comes from the Latin for a group of eight. It is the unit in which nearly all stored data is counted, and the reason it is called an octet rather than a byte is worth knowing.
A byte was originally the number of bits a machine used to hold one character, and that number was not fixed. Early computers used six-bit bytes, some used seven, and a few used nine. The IBM System/360 of 1964 settled on eight and its commercial success made eight the norm, but the word byte kept its older, machine-dependent meaning in specifications where ambiguity was dangerous.
The networking world therefore adopted octet. When a protocol standard says a header field is four octets long, no reader anywhere can interpret that as anything but thirty-two bits. The internet standards published by the IETF use octet throughout for exactly that reason, and French, Romanian and several other languages adopted the word for ordinary use as well, so that a hard disc sold in France is measured in gigaoctets.
Eight bits hold 256 distinct values, which is why so many things come in units of 256. A colour channel runs from 0 to 255. An IPv4 address is four octets, written as four numbers each between 0 and 255. The original ASCII character set used seven bits, leaving one spare, and the various eight-bit extensions that followed each filled that spare bit with a different set of accented letters — the mess that Unicode eventually replaced.
Modern text encoding still counts in octets. UTF-8 uses one octet for the unaccented Latin alphabet, two for most European accented letters and Greek and Cyrillic, three for Chinese, Japanese and Korean, and four for the rest. That is why the same sentence occupies different amounts of storage in different languages, and why a text-length limit measured in octets is not a limit on characters.
Storage capacity, file sizes, memory and network payloads are all quoted in octets or their multiples. Transmission rates are the exception, being quoted in bits per second, and the factor of eight between the two conventions is the single most common source of confusion in the field.
One octet equals 8 bits, 0.008 kilobits, or 0.001 kilooctets.