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
See also: Bit rate

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:

  • 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
  • 125 gigabytes 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

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
Main article: List of interface 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
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See also

Notes
  1. "Penn Researchers Calculate How Much the Eye Tells the Brain". 26 July 2006.
  2. 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
  3. "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.
  4. "Samsung overtakes".

References
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