| Exabits (Ebit) | Tebibits (Tibit) |
|---|---|
| 1 Exabit | 909494.701773 Tibit |
| 2 Exabits | 1818989.40355 Tibit |
| 3 Exabits | 2728484.10532 Tibit |
| 4 Exabits | 3637978.80709 Tibit |
| 5 Exabits | 4547473.50886 Tibit |
| 10 Exabits | 9094947.01773 Tibit |
| 20 Exabits | 18189894.0355 Tibit |
| 25 Exabits | 22737367.5443 Tibit |
| 50 Exabits | 45474735.0886 Tibit |
| 100 Exabits | 90949470.1773 Tibit |
| Reference | Exabits (Ebit) | Tebibits (Tibit) |
|---|---|---|
| A plain text message (160 characters) | 1.28 × 10-15 Ebit | 0.00000000116415 Tibit |
| A three-minute MP3 | 2.4 × 10-11 Ebit | 0.0000218279 Tibit |
| A smartphone photo | 3.2 × 10-11 Ebit | 0.0000291038 Tibit |
| A high-definition film | 0.000000032 Ebit | 0.0291038 Tibit |
| A dual-layer Blu-ray disc | 0.0000004 Ebit | 0.363798 Tibit |
The exabit is a unit of digital information equal to a thousand petabits, or a billion billion bits. Its symbol is Ebit. At this scale no device, no cable and no building is being described. The exabit measures the traffic of whole regions and the output of entire industries over stretches of time.
An exabit is 125 petaoctets. The most common place to meet the unit is in figures for global internet traffic, which are usually given in exaoctets per month. Worldwide traffic passed one exaoctet per month around 2004, reached about a hundred by 2017 and is now several hundred, which in bits is several thousand exabits every month.
Those totals divide in revealing ways. The overwhelming majority is video, and the rest is dominated by software updates, cloud synchronisation and machine-to-machine traffic rather than by anything a person is actively reading. A single popular film released simultaneously worldwide can move a measurable fraction of an exabit in a day.
Storage at this scale exists only as aggregates. The combined capacity of all the hard drives and flash memory manufactured in a year is measured in hundreds of exaoctets, which is thousands of exabits. Estimates of all the data held by humanity at any moment run into the tens of zettaoctets, and the exabit is the unit one step below that in which the components of such estimates are counted.
Scientific instruments produce exabit quantities before any of it is stored. The Square Kilometre Array radio telescope generates raw data at a rate that would fill exaoctets within days, and its design is built around discarding and summarising in real time rather than recording. The same is true of the large particle detectors and of high-resolution climate simulations.
The prefix exa comes from the Greek for six, the exabit being a thousand to the sixth power in bits. It was adopted in 1975 along with peta, at a time when no one expected either to describe anything but astronomical or theoretical quantities. Both are now ordinary units in the technology industry, which says something about how fast the numbers grew.
One exabit equals 1,000 petabits, 125 petaoctets, or about 0.8674 exbibits.
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.