| Kilobits (kbit) | Pebioctets (Pio) |
|---|---|
| 1 Kilobit | 1.11022302463 × 10-13 Pio |
| 2 Kilobits | 2.22044604925 × 10-13 Pio |
| 3 Kilobits | 3.33066907388 × 10-13 Pio |
| 4 Kilobits | 4.4408920985 × 10-13 Pio |
| 5 Kilobits | 5.55111512313 × 10-13 Pio |
| 10 Kilobits | 1.11022302463 × 10-12 Pio |
| 20 Kilobits | 2.22044604925 × 10-12 Pio |
| 25 Kilobits | 2.77555756156 × 10-12 Pio |
| 50 Kilobits | 5.55111512313 × 10-12 Pio |
| 100 Kilobits | 1.11022302463 × 10-11 Pio |
| Reference | Kilobits (kbit) | Pebioctets (Pio) |
|---|---|---|
| A plain text message (160 characters) | 1.28 kbit | 1.42109 × 10-13 Pio |
| A three-minute MP3 | 24000 kbit | 0.00000000266454 Pio |
| A smartphone photo | 32000 kbit | 0.00000000355271 Pio |
| A high-definition film | 32000000 kbit | 0.00000355271 Pio |
| A dual-layer Blu-ray disc | 400000000 kbit | 0.0000444089 Pio |
The kilobit is a unit of digital information equal to one thousand bits. Its symbol is kbit. The lowercase k matters: it marks the decimal kilo of the metric system, one thousand exactly, as distinct from the binary 1,024 that the capital K sometimes indicated in older computing usage.
That distinction was fought over for decades. Memory is built in powers of two, so a chip holding 1,024 bits was called a kilobit chip, and the name stuck even though the number was wrong by 2.4 per cent. Storage and transmission, meanwhile, always counted in true thousands. The IEC settled the matter in 1998 by naming the binary quantity a kibibit, leaving the kilobit to mean one thousand and nothing else.
For a sense of scale, a kilobit holds 125 octets, which is about 125 characters of unaccented text — roughly a long sentence, or the length of a short social-media post. A single low-resolution photograph is thousands of times larger. The kilobit is a unit for things that were once considered generous and are now considered trivially small.
Its historical home was the telephone modem. Dial-up connections were rated in kilobits per second, and the numbers marked the era precisely: 300 bits per second in the late 1970s, then 1.2, 2.4, 9.6, 14.4, 28.8 and finally 56 kilobits per second, the last of which pushed an ordinary voice line to its theoretical ceiling. Anyone who used the internet before broadband measured their experience in these numbers.
The kilobit survives in audio and video encoding, where bit rates are quoted in kilobits per second. Speech codecs used in telephony run from 8 to 64. Music encoded at 128 kilobits per second was the early standard for portable players, 192 and 256 are common now, and 320 is the practical ceiling for the older lossy formats. Video runs a decimal order higher, in megabits.
Memory chip capacities are still occasionally described in kilobits, particularly for small serial memories used in embedded devices, where a 64-kilobit part holds 8 kilooctets of configuration data. In those specifications the figure is usually the binary one, so the datasheet is worth reading carefully.
One kilobit equals 1,000 bits, 125 octets, or about 0.9766 kibibits.
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.