| Terabits per second (Tbit/s) | Exbibits per second (Eibit/s) |
|---|---|
| 1 Terabit per second | 0.000000867361737988 Eibit/s |
| 2 Terabits per second | 0.00000173472347598 Eibit/s |
| 3 Terabits per second | 0.00000260208521397 Eibit/s |
| 4 Terabits per second | 0.00000346944695195 Eibit/s |
| 5 Terabits per second | 0.00000433680868994 Eibit/s |
| 10 Terabits per second | 0.00000867361737988 Eibit/s |
| 20 Terabits per second | 0.0000173472347598 Eibit/s |
| 25 Terabits per second | 0.0000216840434497 Eibit/s |
| 50 Terabits per second | 0.0000433680868994 Eibit/s |
| 100 Terabits per second | 0.0000867361737988 Eibit/s |
| Reference | Terabits per second (Tbit/s) | Exbibits per second (Eibit/s) |
|---|---|---|
| A dial-up modem | 0.000000056 Tbit/s | 4.85723 × 10-14 Eibit/s |
| Typical home broadband | 0.0001 Tbit/s | 8.67362 × 10-11 Eibit/s |
| Gigabit Ethernet | 0.001 Tbit/s | 8.67362 × 10-10 Eibit/s |
| Streaming a 4K film | 0.000025 Tbit/s | 2.1684 × 10-11 Eibit/s |
The terabit per second is a unit of data transfer rate equal to a thousand gigabits per second. Its symbol is Tbit/s. It is the unit of the internet's backbone: the submarine cables, the exchange points and the long-haul optical links that carry traffic between continents.
A single modern transoceanic cable carries several hundred terabits per second. It achieves this not with one enormous channel but with wavelength division multiplexing, which sends dozens of separate colours of light down each fibre at once, and with several fibre pairs in the same cable. Each wavelength carries a few hundred gigabits, and the totals add up.
The historical comparison is worth stating plainly. The first transatlantic telephone cable, laid in 1956, carried thirty-six simultaneous voice calls. A cable laid in the 2020s carries hundreds of terabits per second, enough for hundreds of millions of simultaneous calls. That is a factor of roughly ten million in seventy years, and it was achieved almost entirely by changing what is sent down the glass rather than by laying more cable.
Internet exchange points, where networks meet and hand traffic to one another, publish their throughput in terabits per second. The largest in Europe and Asia peak in the tens of terabits, and those public graphs are among the most reliable measurements of how heavily the internet is being used at a given moment, because they count real traffic rather than capacity.
In octets, a terabit per second is 125 gigaoctets per second — the contents of a large laptop's disc moved every second, continuously. No single storage system can feed such a link; the traffic on these routes is the aggregate of millions of separate connections, each of them tiny by comparison.
Laboratory records go far higher, into petabits per second, using multi-core fibre and hundreds of wavelengths at once, though over short distances under controlled conditions. The gap between what is demonstrated in a laboratory and what is deployed under an ocean has historically been about a decade.
One terabit per second equals 1,000 gigabits per second, 125 gigaoctets per second, or about 0.9095 tebibits per second.
The exbibit per second is a unit of data transfer rate equal to two to the sixtieth power bits per second, which is 1,024 pebibits per second. Its symbol is Eibit/s. It is the binary counterpart of the exabit per second, and the two differ by 15.3 per cent.
That fifteen per cent is more than the margin most engineering work allows anywhere. A quantity stated in the wrong convention at this level is not slightly imprecise but plainly wrong, and no amount of context recovers the intended figure once it has been written ambiguously. This is the situation the IEC prefixes were introduced to prevent.
No physical link approaches this rate. The unit describes aggregates: the total instantaneous traffic of the whole internet is roughly an exabit per second, so a binary exbibit per second is fifteen per cent more than everything moving on every network on the planet at a given moment.
Where a binary figure of this size arises naturally is in address arithmetic rather than in transmission. Two to the sixtieth is a number that appears throughout the design of 64-bit systems, and any rate derived from filling or traversing such an address space in a fixed time is naturally binary. Those calculations are theoretical, but they are the reason the unit is defined rather than left unnamed.
In octets an exbibit per second is 144,115,188,075,855,872, or 128 pebioctets per second. That is more storage moved per second than the world manufactures in several years, which is a way of saying that no source and no destination for such a flow could exist.
For a converter the treatment is mechanical and must be exact. Eibit/s and Ebit/s differ by an eighth, and a tool that treats them as interchangeable has introduced an error larger than the difference between many neighbouring units. The lowercase i is not decoration.
One exbibit per second equals 1,024 pebibits per second, 144,115,188,075,855,872 octets per second, or about 1.153 exabits per second.