| Megabits per second (Mbit/s) | Yobibits per second (Yibit/s) |
|---|---|
| 1 Megabit per second | 8.27180612553 × 10-19 Yibit/s |
| 2 Megabits per second | 1.65436122511 × 10-18 Yibit/s |
| 3 Megabits per second | 2.48154183766 × 10-18 Yibit/s |
| 4 Megabits per second | 3.30872245021 × 10-18 Yibit/s |
| 5 Megabits per second | 4.13590306277 × 10-18 Yibit/s |
| 10 Megabits per second | 8.27180612553 × 10-18 Yibit/s |
| 20 Megabits per second | 1.65436122511 × 10-17 Yibit/s |
| 25 Megabits per second | 2.06795153138 × 10-17 Yibit/s |
| 50 Megabits per second | 4.13590306277 × 10-17 Yibit/s |
| 100 Megabits per second | 8.27180612553 × 10-17 Yibit/s |
| Reference | Megabits per second (Mbit/s) | Yobibits per second (Yibit/s) |
|---|---|---|
| A dial-up modem | 0.056 Mbit/s | 4.63221 × 10-20 Yibit/s |
| Typical home broadband | 100 Mbit/s | 8.27181 × 10-17 Yibit/s |
| Gigabit Ethernet | 1000 Mbit/s | 8.27181 × 10-16 Yibit/s |
| Streaming a 4K film | 25 Mbit/s | 2.06795 × 10-17 Yibit/s |
The megabit per second is a unit of data transfer rate equal to one million bits per second. Its symbol is Mbit/s, often written Mbps. It is the unit in which internet connections are sold, which makes it the data unit most people encounter by name.
Because it is a decimal million and not 1,048,576, the conversion to octets is exact and easy: one megabit per second is 125 kilooctets per second, so a hundred-megabit connection delivers about 12.5 megaoctets per second at best. Anyone who watches a file transfer and does the division has understood the entire relationship between how connections are advertised and how transfers are reported.
What a household actually needs is far below what it usually buys. Standard-definition video streaming uses about 3 megabits per second, high definition about 5, and ultra-high definition about 25. A video call is around 3 to 8. A large family watching four separate high-definition streams while somebody downloads a game is using perhaps 60 megabits per second, which a hundred-megabit connection handles comfortably.
The reason to buy more capacity than that is not peak speed but behaviour under load. A link that is near its limit develops queues, and queues add delay, which shows up as stutter in video calls and lag in games. A connection with generous headroom keeps its latency low, and that is a more noticeable improvement than a higher number on a speed test.
Wired local networks pass through this range on the way up. The original Ethernet ran at 10 megabits per second, its successor at 100, and both were the standard office connection for a decade each before gigabit replaced them. Wireless standards followed the same path with a lag, and both are now measured in hundreds of megabits or in gigabits.
Real throughput is always below the nominal rate. Protocol overhead takes 5 to 10 per cent on a wired link; a shared wireless channel loses much more, because the medium is divided between all the devices using it and interference forces retransmission. A connection advertised at 100 megabits per second measured at 90 over cable and 50 over a busy wireless network is behaving normally.
One megabit per second equals 1,000,000 bits per second, 125 kilooctets per second, or about 0.9537 mebibits per second.
The yobibit per second is a unit of data transfer rate equal to two to the eightieth power bits per second, which is 1,024 zebibits per second. Its symbol is Yibit/s. It is the largest binary transfer rate the International Electrotechnical Commission has named, and the binary counterpart of the yottabit per second.
At this final step the binary and decimal conventions differ by 20.9 per cent, and that number is the conclusion of the argument the IEC prefixes were created to settle. A naming habit that was 2.4 per cent wrong at the kibibit has grown, through eight successive multiplications by 1.024, into a discrepancy of more than a fifth. No measurement system can carry an ambiguity that large.
The unit describes nothing. Global internet traffic runs at roughly an exabit per second, so a yobibit per second is over a million times the total communication of the human species. No link, no aggregate and no forecast reaches it, and none is expected to.
The binary series stops here because the decimal series stopped at yotta when the IEC standard was written in 1998. When ronna and quetta were added to the metric system in 2022, no matching binary names were defined, so a rate of two to the ninetieth bits per second has no accepted short form. That gap will presumably be filled if it is ever needed, which at present it is not.
Defining a rung of a ladder nobody has climbed still has a purpose. A system whose names run out forces its users to improvise, and improvised extensions conflict; writing the whole series out in advance means the rule, rather than a table of exceptions, is all anyone has to learn. That is the same reasoning that gave the metric system its complete prefix set.
For any reader of technical material the lesson of the whole binary series is a single character. Kibit/s, Mibit/s, Gibit/s, Tibit/s, Pibit/s, Eibit/s, Zibit/s and Yibit/s are binary; kbit/s, Mbit/s, Gbit/s, Tbit/s, Pbit/s, Ebit/s, Zbit/s and Ybit/s are decimal; and the difference between them widens from a rounding error to a fifth as you climb.
One yobibit per second equals 1,024 zebibits per second, 151,115,727,451,828,646,838,272 octets per second, or about 1.209 yottabits per second.