In telecommunications, **data transfer rate** is the average number of bits (bitrate), characters or symbols (baudrate), or blocks per unit time passing between equipment in a data transmission system. Most commonly, measurements of data transfer rate are reported in multiples of unit bits per second (bit/s) or occasionally in bytes per second (B/s). The data rates of modern residential high-speed Internet connections are most commonly expressed in multiples of bits per second, such as megabits per second (Mbit/s) or kilobits per second (kbit/s).

## Standards for unit symbols and prefixes

See also: *Bit rate* for the differences between gross bitrate and net bitrate and between throughput and goodput.

### Unit symbol

The ISQ symbols for the bit and byte are *bit* and *B*, respectively. In the context of data rate units, one byte consists of 8 bits, and is synonymous with the unit octet. The abbreviation bps is often used to mean bit/s, so that when a *1 Mbps* connection is advertised, it usually means that the maximum achievable bandwidth is 1 Mbit/s (one million bits per second), which is 0.125 MB/s (megabyte per second), or about 0.1192 MiB/s (mebibyte per second). The Institute of Electrical and Electronics Engineers (IEEE) uses the symbol b for bit.

### Prefix

In both the SI and ISQ, the prefix k stands for kilo, meaning 1,000, while Ki is the symbol for the binary prefix kibi-, meaning 1,024. The binary prefixes were introduced in 1998 by the International Electrotechnical Commission (IEC) and in IEEE 1541-2002 which was reaffirmed on 27 March 2008. The letter K is often used as a non-standard abbreviation for 1,024, especially in "KB" to mean KiB, the kilobyte in its binary sense.

### Variations

In 1999, the IEC published Amendment 2 to "IEC 60027-2: Letter symbols to be used in electrical technology – Part 2: Telecommunications and electronics." This standard, approved in 1998, introduced the prefixes kibi-, mebi-, gibi-, tebi-, pebi-, and exbi- to be used in specifying binary multiples of a quantity. The name is derived from the first two letters of the original SI prefixes followed by bi (short for *binary*). It also clarifies that the SI prefixes be used only to mean powers of 10 and never powers of 2.

## Decimal multiples of bits

These units are often used in a manner inconsistent with the IEC standard. See above section titled "variations".

### Kilobit per second

**kilobit per second** (symbol **kbit/s** or **kb/s**, often abbreviated "kbps") is a unit of data transfer rate equal to:

- 1,000 bits per second
- 125 bytes per second

### Megabit per second

**megabit per second** (symbol **Mbit/s** or **Mb/s**, often abbreviated "Mbps") is a unit of data transfer rate equal to:

- 1,000,000 bits per second
- 1,000 kilobits per second
- 125,000 bytes per second
- 125 kilobytes per second

### Gigabit per second

**gigabit per second** (symbol **Gbit/s** or **Gb/s**, often abbreviated "Gbps") is a unit of data transfer rate equal to:

- 1,000 megabits per second
- 1,000,000 kilobits per second
- 1,000,000,000 bits per second
- 125,000,000 bytes per second

### Terabit per second

**terabit per second** (symbol **Tbit/s** or **Tb/s**, sometimes abbreviated "Tbps") is a unit of data transfer rate equal to:

- 1,000 gigabits per second
- 1,000,000 megabits per second
- 1,000,000,000 kilobits per second
- 1,000,000,000,000 bits per second
- 125,000,000,000 bytes per second

## Binary multiples of bits

For more details on prefixes such as kibi, mebi, gibi, tebi, see Binary prefix.

The prefix name for binary prefixes (e.g., "kibi") is not capitalized, but the prefix symbol (e.g. "Ki") is.

### Kibibit per second

The kibibit per second (**Kibit/s**) is a unit of data transfer rate equal to:

- 1,024 bits per second

### Mebibit per second

The mebibit per second (**Mibit/s**) is a unit of data transfer rate equal to:

- 1,048,576 bits per second
- 1,024 kibibits per second

### Gibibit per second

The gibibit per second (**Gibit/s**) is a unit of data transfer rate equal to:

- 1,073,741,824 bits per second
- 1,048,576 kibibits per second
- 1,024 mebibits per second

### Tebibit per second

The tebibit per second (**Tibit/s**) is a unit of data transfer rate equal to:

- 1,099,511,627,776 bits per second
- 1,073,741,824 kibibits per second
- 1,048,576 mebibits per second
- 1,024 gibibits per second

## Decimal multiples of bytes

These units are often not used in the suggested ways! See above section titled "variations".

### Kilobyte per second

**kilobyte per second** (**kB/s**) is a unit of data transfer rate equal to:

- 8,000 bits per second
- 1,000 bytes per second
- 8 kilobits per second

### Megabyte per second

**megabyte per second** (**MB/s**) is a unit of data transfer rate equal to:

- 8,000,000 bits per second
- 1,000,000 bytes per second
- 1,000 kilobytes per second
- 8 megabits per second

### Gigabyte per second

**gigabyte per second** (**GB/s**) is a unit of data transfer rate equal to:

- 8,000,000,000 bits per second
- 1,000,000,000 bytes per second
- 1,000,000 kilobytes per second
- 1,000 megabytes per second
- 8 gigabits per second

### Terabyte per second

**terabyte per second** (**TB/s**) is a unit of data transfer rate equal to:

- 8,000,000,000,000 bits per second
- 1,000,000,000,000 bytes per second
- 1,000,000,000 kilobytes per second
- 1,000,000 megabytes per second
- 1,000 gigabytes per second
- 8 terabits per second

## Binary multiples of bytes

For more details on prefixes such as kibi-, mebi-, gibi-, and tebi-, see Binary prefix.

### Kibibyte per second

The kibibyte per second (**KiB/s**) is a unit of data transfer rate equal to:

- 1,024 bytes per second
- 8 kibibits per second
- 8192 bits per second

### Mebibyte per second

The mebibyte per second (**MiB/s**) is a unit of data transfer rate equal to:

- 1,048,576 bytes per second
- 1,024 kibibytes per second
- 8 mebibits per second
- 8192 kibibits per second
- 8,388,608 bits per second

### Gibibyte per second

The gibibyte per second (**GiB/s**) is a unit of data transfer rate equal to:

- 1,073,741,824 bytes per second
- 1,048,576 kibibytes per second
- 1,024 mebibytes per second
- 8 gibibits per second
- 8192 mebibits per second
- 8,388,608 kibibits per second
- 8,589,934,592 bits per second

### Tebibyte per second

The tebibyte per second (**TiB/s**) is a unit of data transfer rate equal to:

- 1,099,511,627,776 bytes per second
- 1,073,741,824 kibibytes per second
- 1,048,576 mebibytes per second
- 1,024 gibibytes per second
- 8 tebibits per second
- 8192 gibibits per second
- 8,388,608 mebibits per second
- 8,589,934,592 kibibits per second
- 8,796,093,022,208 bits per second

## Conversion table

Name | Symbol | bit per second | byte per second | bit per second (formula) | byte per second (formula) |
---|---|---|---|---|---|

bit per second | bit/s | 1 | 0.125 | 1 | 1/8 |

byte per second | B/s | 8 | 1 | 8 | 1 |

kilobit per second | kbit/s | 1,000 | 125 | 10^{3} | 10^{3}/8 |

kibibit per second | Kibit/s | 1,024 | 128 | 2^{10} | 2^{7} |

kilobyte per second | kB/s | 8,000 | 1,000 | 8x10^{3} | 10^{3} |

kibibyte per second | KiB/s | 8,192 | 1,024 | 2^{13} | 2^{10} |

megabit per second | Mbit/s | 1,000,000 | 125,000 | 10^{6} | 10^{6}/8 |

mebibit per second | Mibit/s | 1,048,576 | 131,072 | 2^{20} | 2^{17} |

megabyte per second | MB/s | 8,000,000 | 1,000,000 | 8x10^{6} | 10^{6} |

mebibyte per second | MiB/s | 8,388,608 | 1,048,576 | 2^{23} | 2^{20} |

gigabit per second | Gbit/s | 1,000,000,000 | 125,000,000 | 10^{9} | 10^{9}/8 |

gibibit per second | Gibit/s | 1,073,741,824 | 134,217,728 | 2^{30} | 2^{27} |

gigabyte per second | GB/s | 8,000,000,000 | 1,000,000,000 | 8x10^{9} | 10^{9} |

gibibyte per second | GiB/s | 8,589,934,592 | 1,073,741,824 | 2^{33} | 2^{30} |

terabit per second | Tbit/s | 1,000,000,000,000 | 125,000,000,000 | 10^{12} | 10^{12}/8 |

tebibit per second | Tibit/s | 1,099,511,627,776 | 137,438,953,472 | 2^{40} | 2^{37} |

terabyte per second | TB/s | 8,000,000,000,000 | 1,000,000,000,000 | 8x10^{12} | 10^{12} |

tebibyte per second | TiB/s | 8,796,093,022,208 | 1,099,511,627,776 | 2^{43} | 2^{40} |

## Examples of bit rates

Main article: List of device bit rates

Quantity | Unit | bits per second | bytes per second | Field | Description |
---|---|---|---|---|---|

56 | kbit/s | 56,000 | 7,000 | Networking | 56kbit modem – 56 kbit/s – 56,000 bit/s |

64 | kbit/s | 64,000 | 8,000 | Networking | 64kbit/s in an ISDN B channel or best quality, uncompressed telephone line. |

1,536 | kbit/s | 1,536,000 | 192,000 | Networking | 24 channels of telephone in the US, or a good VTC T1. |

10 | Mbit/s | 10,000,000 | 1,250,000 | Networking | 10^{7} bit/s is the speed of classic Ethernet: 10BASE2, 10BASE5, 10BASE-T |

10 | Mbit/s | 10,000,000 | 1,250,000 | Biology | Research suggests that the human retina transmits data to the brain at the rate of ca. 10^{7} bit/se^{} |

54 | Mbit/s | 54,000,000 | 6,750,000 | Networking | 802.11g, Wireless G LAN |

100 | Mbit/s | 100,000,000 | 12,500,000 | Networking | Fast Ethernet |

600 | Mbit/s | 600,000,000 | 75,000,000 | Networking | 802.11n, Wireless N LAN |

10 | Gbit/s | 10,000,000,000 | 1,250,000,000 | Networking | 10 Gigabit Ethernet |

100 | Gbit/s | 100,000,000,000 | 12,500,000,000 | Networking | 100 Gigabit Ethernet |

1 | Tbit/s | 1,000,000,000,000 | 125,000,000,000 | Networking | SEA-ME-WE 4 submarine communications cable – 1.28 terabits per second |

4 | kbit/s | 4,000 | 500 | Audio data | minimum achieved for encoding recognizable speech (using special-purpose speech codecs) |

8 | kbit/s | 8,000 | 1,000 | Audio data | low bit rate telephone quality |

32 | kbit/s | 32,000 | 4,000 | Audio data | MW quality and ADPCM voice in telephony, doubling the capacity of a 30 chan link to 60 ch. |

128 | kbit/s | 128,000 | 16,000 | Audio data | 128 kbit/s MP3 – 128,000 bit/s |

192 | kbit/s | 192,000 | 24,000 | Audio data | 192 kbit/s MP3 – 192,000 bit/s |

1,411.2 | kbit/s | 1,411,200 | 176,400 | Audio data | CD audio (uncompressed, 16 bit samples × 44.1 kHz × 2 channels) |

2 | Mbit/s | 2,000,000 | 250,000 | Video data | 30 channels of telephone audio or a Video Tele-Conference at VHS quality |

8 | Mbit/s | 8,000,000 | 1,000,000 | Video data | DVD quality |

27 | Mbit/s | 27,000,000 | 3,375,000 | Video data | HDTV quality |

1.244 | Gbit/s | 1,244,000,000 | 155,500,000 | Networking | OC-24, a 1.244 Gbit/s SONET data channel |

9.953 | Gbit/s | 9,953,000,000 | 1,244,125,000 | Networking | OC-192, a 9.953 Gbit/s SONET data channel |

39.813 | Gbit/s | 39,813,000,000 | 4,976,625,000 | Networking | OC-768, a 39.813 Gbit/s SONET data channel, the fastest in current use |

60 | MB/s | 480,000,000 | 60,000,000 | Computer data interfaces | USB 2.0 High-Speed |

98.3 | MB/s | 786,432,000 | 98,304,000 | Computer data interfaces | FireWire IEEE 1394b-2002 S800 |

120 | MB/s | 960,000,000 | 120,000,000 | Computer data interfaces | Harddrive read, Samsung SpinPoint F1 HD103Uj |

133 | MB/s | 1,064,000,000 | 133,000,000 | Computer data interfaces | Parallel ATA UDMA 6 |

133 | MB/s | 1,064,000,000 | 133,000,000 | Computer data interfaces | PCI 32-bit at 33 MHz (standard configuration) |

188 | MB/s | 1,504,000,000 | 188,000,000 | Computer data interfaces | SATA I 1.5 Gbit/s – First generation |

375 | MB/s | 3,000,000,000 | 375,000,000 | Computer data interfaces | SATA II 3Gbit/s – Second generation |

500 | MB/s | 4,000,000,000 | 500,000,000 | Computer data interfaces | PCI Express x1 v2.0 |

625 | MB/s | 5,000,000,000 | 625,000,000 | Computer data interfaces | USB 3.0 SuperSpeed |

750 | MB/s | 6,000,000,000 | 750,000,000 | Computer data interfaces | SATA III 6 Gbit/s – Third generation |

1067 | MB/s | 8,533,333,333 | 1,066,666,667 | Computer data interfaces | PCI-X 64 bit 133 MHz |

1250 | MB/s | 10,000,000,000 | 1,250,000,000 | Computer data interfaces | Thunderbolt |

2500 | MB/s | 20,000,000,000 | 2,500,000,000 | Computer data interfaces | Thunderbolt 2 |

8000 | MB/s | 64,000,000,000 | 8,000,000,000 | Computer data interfaces | PCI Express x16 v2.0 |

12000 | MB/s | 96,000,000,000 | 12,000,000,000 | Computer data interfaces | InfiniBand 12X QDR |

16000 | MB/s | 128,000,000,000 | 16,000,000,000 | Computer data interfaces | PCI Express x16 v3.0 |