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Data-rate units

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Bit rates (data-rate units)
Name Symbol Multiple
bit per second bit/s 1 1
Metric 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

In telecommunications, data rate units are commonly 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). They are used as units of measurement for expressing data transfer rate, the average number of bits (bit rate), characters or symbols (symbol rate), or data blocks per unit time passing through a communication link in a data-transmission system.

Standards for unit symbols and prefixes

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See also: Bit rate

Unit symbol

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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

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In both the SI and ISQ, the prefix k stands for kilo, meaning 1000, while Ki is the symbol for the binary prefix kibi-, meaning 1024. 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

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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

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These units are often used in a manner inconsistent with the IEC standard.

Kilobit per second

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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

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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

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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

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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

Petabit per second

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Petabit per second (symbol Pbit/s or Pb/s, sometimes abbreviated "Pbps") is a unit of data transfer rate equal to:

  • 1,000 terabits per second
  • 1,000,000 gigabits per second
  • 1,000,000,000 megabits per second
  • 1,000,000,000,000 kilobits per second
  • 1,000,000,000,000,000 bits per second
  • 125,000,000,000,000 bytes per second
  • 125 terabytes per second

Decimal multiples of bytes

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These units are often not used in the suggested ways; see § Variations.

Kilobyte per second

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kilobyte per second (kB/s) (sometimes abbreviated "kBps") 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

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megabyte per second (MB/s) (can be abbreviated as MBps) 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

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gigabyte per second (GB/s) (can be abbreviated as GBps) 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

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terabyte per second (TB/s) (can be abbreviated as TBps) 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