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In telecommunications, bit rate or data transfer rate is the average number of bits, characters, or blocks per unit time passing between equipment in a data transmission system. This is typically measured in multiples of the unit bits per second or occasionally in bytes per second. Various other units may also be used to measure the data rate. Currently, the most common modern residential high-speed Internet connection is measured in bits (not bytes) per second. The distinction between bits and bytes, while important, remains as a cause for some confusion amongst many of the non-technically knowledgeable.

Bit rates
Name Symbol Multiple
Decimal prefixes (SI)
kilobit per second kbit/s 103
megabit per second Mbit/s 106
gigabit per second Gbit/s 109
terabit per second Tbit/s 1012
Binary prefixes (IEC 60027-2)
kibibit per second Kibit/s 210
mebibit per second Mibit/s 220
gibibit per second Gibit/s 230
tebibit per second Tibit/s 240

Standards for unit symbols and prefixes

To be as explicit as possible, both the prefix (M or Mi) and the unit (b or B) must be known. For example, the abbreviation 2 Mb can actually be expanded in 4 different ways (mega- vs mebi- and -bit vs -byte):

Unit Bits Bits / 1,000,000
Mega-bit 1,000,000 1.0
Mebi-bit 1,048,576 1.05
Mega-byte 8,000,000 8.0
Mebi-byte 8,388,608 8.39

The table above shows an approximate 5% difference between the corresponding mega- and mebi- prefixes with a 800% difference between bit and byte units.

Unit symbol: b vs B

b is the IEEE standard symbol for bit and B is the standard symbol for byte. In the context of data rate units, one byte refers to 8 bits. For example, when a 1 Mb/s connection is advertised, it usually means that the maximum achievable download bandwidth is 1 megabit/s (million bits per second), which is 0.125 MB/s (megabyte per second), or about 0.1192 MiB/s (mebibyte per second).

Prefix: k vs Ki

k- stands for kilo, meaning 1,000, while Ki- stands for kilobinary ("kibi-"), meaning 1,024. The standardized binary prefixes such as Ki- were relatively recently introduced (in IEEE 1541-2002 that was reaffirmed on 27 March 2008). K- is often used to mean 1,024, especially in KB, the kilobyte in its binary sense.


In 1999, the International Electrotechnical Commission (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

A kilobit per second -kbps, kbit/s, or kb/s- is a unit of data transfer rate equal to:

  • 1,000 bits per second or
  • 125 bytes per second.

Megabit per second

A megabit per second -Mbps, Mbit/s, or Mb/s- (not to be confused with MBps, or MB/s, which would be megabytes per second: also not to be confused with mbit/s which would be millibits per second: also not to be confused with Mbitpps which would be megabits per picosecond) is a unit of data transfer rate equal to:

  • 1,000,000 bits per second or
  • 1,000 kilobits per second or
  • 125,000 bytes per second or
  • 125 kilobytes per second.

Gigabit per second

A gigabit per second -Gbps, Gbit/s, or Gb/s- is a unit of data transfer rate equal to:

  • 1,000 megabits per second or
  • 1,000,000 kilobits per second or
  • 1,000,000,000 bits per second or
  • 125,000,000 bytes per second.

Terabit per second

A terabit per second -Tbps, Tbit/s, or Tb/s- is a unit of data transfer rate equal to:

  • 1,000 gigabits per second or
  • 1,000,000 megabits per second or
  • 1,000,000,000 kilobits per second or
  • 1,000,000,000,000 bits per second or
  • 125,000,000,000 bytes per second.

Binary multiples of bits

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

Kibibit per second

A kibibit per second (Kibit/s or Kib/s) is a unit of data transfer rate equal to:

  • 1,024 bits per second.

Mebibit per second

A mebibit per second (Mibit/s or Mib/s) is a unit of data transfer rate equal to:

  • 1,048,576 bits per second or
  • 1,024 kibibits per second.

Gibibit per second

A gibibit per second (Gibit/s or Gib/s) is a unit of data transfer rate equal to:

  • 1,073,741,824 bits per second or
  • 1,048,576 kibibits per second or
  • 1,024 mebibits per second.

Tebibit per second

A tebibit per second (Tibit/s or Tib/s) is a unit of data transfer rate equal to:

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

Decimal multiples of bytes

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

Kilobyte per second

A kilobyte per second -kBps or kB/s- is a unit of data transfer rate equal to:

  • 8,000 bits per second, or
  • 1,000 bytes per second, or
  • 8 kilobits per second.

Megabyte per second

A megabyte per second -MBps or MB/s- (not to be confused with Mbps or Mb/s, which would be megabits per second) is a unit of data transfer rate equal to:

  • 8,000,000 bits per second, or
  • 1,000,000 bytes per second, or
  • 1,000 kilobytes per second, or
  • 8 megabits per second.

Gigabyte per second

A gigabyte per second -GBps or GB/s- is a unit of data transfer rate equal to:

  • 8,000,000,000 bits per second, or
  • 1,000,000,000 bytes per second, or
  • 1,000,000 kilobytes per second, or
  • 1,000 megabytes per second, or
  • 8 gigabits per second.

Terabyte per second

A terabyte per second -TBps or TB/s- is a unit of data transfer rate equal to:

  • 8,000,000,000,000 bits per second, or
  • 1,000,000,000,000 bytes per second, or
  • 1,000,000,000 kilobytes per second, or
  • 1,000,000 megabytes per second, or
  • 1,000 gigabytes per second, or
  • 8 terabits per second.

Binary multiples of bytes

Kibibyte per second

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

  • 1,024 bytes per second, or
  • 8 kibibits per second, or
  • 8192 bits per second.

Mebibyte per second

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

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

Gibibyte per second

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

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

Tebibyte per second

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

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

Conversion formula

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 1,000 125 103 103/8
kibibit per second Kibit/s 1,024 128 210 27
kilobyte per second kB/s 8,000 1,000 8x103 103
kibibyte per second KiB/s 8,192 1,024 213 210
megabit per second Mbit/s 1,000,000 125,000 106 106/8
mebibit per second Mibit/s 1,048,576 131,072 220 217
megabyte per second MB/s 8,000,000 1,000,000 8x106 106
mebibyte per second MiB/s 8,388,608 1,048,576 223 220
gigabit per second Gbit/s 1,000,000,000 125,000,000 109 109/8
gibibit per second Gibit/s 1,073,741,957 134,217,728 230 227
gigabyte per second GB/s 8,000,000,000 1,000,000,000 8x109 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 1012/8
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 8x1012 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 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 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/sec[1]
1 Gbit/s 1,000,000,000 125,000,000 Networking Gigabit Ethernet
10 Gbit/s 10,000,000,000 1,250,000,000 Networking 10 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 [2]
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
625 MB/s 5,000,000,000 625,000,000 Computer data interfaces USB 3.0 SuperSpeed
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 [3]
133 MB/s 1,064,000,000 133,000,000 Computer data interfaces Parallel ATA UDMA 6
188 MB/s 1,504,000,000 188,000,000 Computer data interfaces SATA 1.5Gbit/s – First generation
375 MB/s 3,000,000,000 375,000,000 Computer data interfaces SATA 3Gbit/s – Second generation
750 MB/s 6,000,000,000 750,000,000 Computer data interfaces SATA 6Gbit/s – Third generation
1067 MB/s 5,533,333,333 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
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



  • International Electrotechnical Commission (2007). "Prefixes for binary multiples". Retrieved on 2007-05-06.
  • IEC 60027-2 "Letter symbols to be used in electrical technology – Part 2: Telecommunications and electronics+
  • Donald Knuth: "What is a kilobyte?"
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