| Petabits (Pbit) | Tebibits (Tibit) |
|---|---|
| 1 Petabit | 909.494701773 Tibit |
| 2 Petabits | 1818.98940355 Tibit |
| 3 Petabits | 2728.48410532 Tibit |
| 4 Petabits | 3637.97880709 Tibit |
| 5 Petabits | 4547.47350886 Tibit |
| 10 Petabits | 9094.94701773 Tibit |
| 20 Petabits | 18189.8940355 Tibit |
| 25 Petabits | 22737.3675443 Tibit |
| 50 Petabits | 45474.7350886 Tibit |
| 100 Petabits | 90949.4701773 Tibit |
| Reference | Petabits (Pbit) | Tebibits (Tibit) |
|---|---|---|
| A plain text message (160 characters) | 1.28 × 10-12 Pbit | 0.00000000116415 Tibit |
| A three-minute MP3 | 0.000000024 Pbit | 0.0000218279 Tibit |
| A smartphone photo | 0.000000032 Pbit | 0.0000291038 Tibit |
| A high-definition film | 0.000032 Pbit | 0.0291038 Tibit |
| A dual-layer Blu-ray disc | 0.0004 Pbit | 0.363798 Tibit |
The petabit is a unit of digital information equal to a thousand terabits, or a million billion bits. Its symbol is Pbit. It sits at the boundary between quantities that are routinely deployed and quantities that still belong to research laboratories and to totals aggregated across whole networks.
A petabit is 125 teraoctets. That is the storage of roughly a hundred and twenty-five large consumer hard drives, or in more everyday terms about thirty thousand hours of high-definition video — three and a half years of continuous viewing. No single device holds a petabit; the figure describes systems rather than objects.
The most striking use of the unit is in optical transmission records. Research groups in Japan, the Netherlands and elsewhere have carried more than a petabit per second down a single strand of fibre, achieved by combining multi-core fibre — several light-guiding paths inside one cladding — with hundreds of separate wavelengths and advanced modulation. Those results run over tens of kilometres in the laboratory, not the thousands of kilometres a working sea cable must cross.
At the network level the petabit describes aggregate capacity. The total interconnect capacity of a large data centre, the combined capacity of all cables landing on a continent, and the peak throughput of the largest content networks are all quoted in petabits per second. These are sums over many links rather than the rating of any one of them.
Storage systems reach petabit scale too, though they are always labelled in octets. A large scientific archive holding a hundred petaoctets is holding eight hundred petabits, and facilities of that size exist for genomics, particle physics and astronomical survey data. The particle detectors at CERN discard the vast majority of what they see precisely because keeping it would exceed even these capacities.
The prefix peta comes from the Greek for five, because a petabit is a thousand raised to the fifth power in bits. That naming pattern continues upward with exa for six and zetta for seven, so the ladder above the petabit is regular and easy to extend.
One petabit equals 1,000,000,000,000,000 bits, 1,000 terabits, 125 teraoctets, or about 0.8882 pebibits.
The tebibit is a unit of digital information equal to 1,099,511,627,776 bits, which is 1,024 gibibits or two to the fortieth power. Its symbol is Tibit. It is the binary counterpart of the terabit, and the two now differ by 10 per cent, the point at which the distinction stops being pedantic and starts being financial.
That ten per cent is the reason the IEC prefixes exist. At the kibibit the discrepancy was 2.4 per cent and could be waved away; here it is a tenth of the quantity. In a contract for storage hardware, in a service agreement that guarantees capacity, or in a specification that a supplier must meet, a tenth is the difference between compliance and breach.
The unit's real home is flash memory, where dies are now made with capacities of one tebibit and above by stacking cell layers vertically. A modern flash die may hold a tebibit or two, and a package containing eight of them holds a teraoctet of raw capacity, from which spare blocks and management overhead are subtracted before anything reaches the user.
A tebibit is 137,438,953,472 octets, or 128 gibioctets. In practical terms it is the storage of a mid-range phone, or a couple of hours of uncompressed high-resolution video. The unit describes the raw material of storage devices rather than anything a person handles directly.
Filesystems also count in binary at this scale. A volume reported as 16 tebibytes by one tool and 17.6 terabytes by another is the same volume, and the difference is entirely in the base of the arithmetic. Anyone administering storage learns to check which convention a tool uses before comparing two numbers from different sources.
Correct notation is Tibit, with the capital T and lowercase i. It appears in flash memory datasheets, in filesystem documentation and in standards, and almost nowhere else. The presence of that lowercase i is the only reliable signal that a figure is binary, which is why careful technical writing uses it even when the difference seems small.
One tebibit equals 1,099,511,627,776 bits, 1,024 gibibits, 137,438,953,472 octets, or about 1.100 terabits.