Data-rate units
In telecommunications, data-transfer rate is the average number of bits (bitrate), characters or symbols (baudrate), or data blocks per unit time passing through a communication link in a data-transmission system. Common data rate units are multiples of bits per second (bit/s) and bytes per second (B/s). For example, the data rates of modern residential high-speed Internet connections are commonly expressed in megabits per second (Mbit/s).
| Bit rates | |||
|---|---|---|---|
| Name | Symbol | Multiple | |
| bit per second | bit/s | 1 | 1 |
| Decimal prefixes (SI) | |||
| kilobit per second | kbit/s | 103 | 10001 |
| megabit per second | Mbit/s | 106 | 10002 |
| gigabit per second | Gbit/s | 109 | 10003 |
| terabit per second | Tbit/s | 1012 | 10004 |
| Binary prefixes (IEC 80000-13) | |||
| kibibit per second | Kibit/s | 210 | 10241 |
| mebibit per second | Mibit/s | 220 | 10242 |
| gibibit per second | Gibit/s | 230 | 10243 |
| tebibit per second | Tibit/s | 240 | 10244 |
Standards for unit symbols and prefixes
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.
Unit prefixes
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. In the context of data rates, however, typically only decimal prefixes are used, and they have their standard SI interpretation.
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 are 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.
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 kilobits per second
- 1,000,000 bits 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
- 125 megabytes 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:
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
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 | 103 | 1/8 × 103 |
| kibibit per second | Kibit/s | 1,024 | 128 | 210 | 27 |
| kilobyte per second | kB/s | 8,000 | 1,000 | 8 × 103 | 103 |
| kibibyte per second | KiB/s | 8,192 | 1,024 | 213 | 210 |
| megabit per second | Mbit/s | 1,000,000 | 125,000 | 106 | 1/8 × 106 |
| mebibit per second | Mibit/s | 1,048,576 | 131,072 | 220 | 217 |
| megabyte per second | MB/s | 8,000,000 | 1,000,000 | 8 × 106 | 106 |
| mebibyte per second | MiB/s | 8,388,608 | 1,048,576 | 223 | 220 |
| gigabit per second | Gbit/s | 1,000,000,000 | 125,000,000 | 109 | 1/8 × 109 |
| gibibit per second | Gibit/s | 1,073,741,824 | 134,217,728 | 230 | 227 |
| gigabyte per second | GB/s | 8,000,000,000 | 1,000,000,000 | 8 × 109 | 109 |
| gibibyte per second | GiB/s | 8,589,934,592 | 1,073,741,824 | 233 | 230 |
| terabit per second | Tbit/s | 1,000,000,000,000 | 125,000,000,000 | 1012 | 1/8 × 1012 |
| tebibit per second | Tibit/s | 1,099,511,627,776 | 137,438,953,472 | 240 | 237 |
| terabyte per second | TB/s | 8,000,000,000,000 | 1,000,000,000,000 | 8 × 1012 | 1012 |
| tebibyte per second | TiB/s | 8,796,093,022,208 | 1,099,511,627,776 | 243 | 240 |
Examples of 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 | 64 kbit/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 | 107 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. 107 bit/s[1] [2] |
| 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 |
| 1 | Gbit/s | 1,000,000,000 | 125,000,000 | Networking | 1 Gigabit Ethernet |
| 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[3] |
| 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[4] |
| 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 |
| 5.0 | Gbit/s | 5,000,000,000 | 625,000,000 | Computer data interfaces | USB 3.0 SuperSpeed - a.k.a. USB 3.1 Gen1 |
| 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 |
| 10 | Gbit/s | 10,000,000,000 | 1,250,000,000 | Computer data interfaces | USB 3.1 SuperSpeed+ - a.k.a. USB 3.1 Gen2 |
| 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 |
| 5000 | MB/s | 40,000,000,000 | 5,000,000,000 | Computer data interfaces | Thunderbolt 3 |
| 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 |
See also
- Binary prefix
- Bit rate
- List of device bandwidths
- Orders of magnitude (bit rate)
- Orders of magnitude (data)
- SI prefix
Notes
- "Penn Researchers Calculate How Much the Eye Tells the Brain". 26 July 2006.
- Koch K, J McLean, R Segev, MA Freed, MJ Berry II, V Balasubramanian, P Sterling. 2006. How much the eye tells the brain. Current Biology 16:1428-1434., 26 July 2006
- "Fujitsu Completes Construction of SEA-ME-WE 4 Submarine Cable Network". Fujitsu Press Releases. Fujitsu. 2005-12-13. Archived from the original on 2007-03-17. Retrieved 2008-01-31.
- "Samsung overtakes".
References
- International Electrotechnical Commission (2007). "Prefixes for binary multiples" (archived). Retrieved on 2007-05-06. - updated page lacks table but now references IEC 80000-13:2008 rather than IEC 60027-2.
- IEC 60027-2 "Letter symbols to be used in electrical technology – Part 2: Telecommunications and electronics+
- Donald Knuth: "What is a kilobyte?"