Data rate units

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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 80000-13)
kibibit per second Kibit/s 210
mebibit per second Mibit/s 220
gibibit per second Gibit/s 230
tebibit per second Tibit/s 240

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 a cause for confusion.

Standards for unit symbols and prefixes[edit]

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 an 800% difference between bit and byte units.

Unit symbol: b vs B[edit]

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[edit]

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.

Variations[edit]

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[edit]

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

Kilobit per second[edit]

A kilobit per secondkbit/s, kbps, or kb/s – is a unit of data transfer rate equal to:

  • 1000 bits per second
  • 125 bytes per second

Megabit per second[edit]

A megabit per secondMbit/s, Mbps, or Mb/s – (not to be confused with MBps, or MB/s, which would be megabytes per second) 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[edit]

A gigabit per secondGbit/s, Gbps, or Gb/s – 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[edit]

A terabit per secondTbit/s, Tbps, or Tb/s – 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[edit]

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[edit]

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[edit]

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

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

Gibibit per second[edit]

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
  • 1,048,576 kibibits per second
  • 1,024 mebibits per second

Tebibit per second[edit]

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
  • 1,073,741,824 kibibits per second
  • 1,048,576 mebibits per second
  • 1,024 gibibits per second

Decimal multiples of bytes[edit]

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

Kilobyte per second[edit]

A kilobyte per secondkBps or 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[edit]

A megabyte per secondMBps 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
  • 1,000,000 bytes per second
  • 1,000 kilobytes per second
  • 8 megabits per second

Gigabyte per second[edit]

A gigabyte per secondGBps or 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[edit]

A terabyte per secondTBps or 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[edit]

Kibibyte per second[edit]

A 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[edit]

A 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[edit]

A 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[edit]

A 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[edit]

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[edit]

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
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 1.5Gbit/s – First generation
375 MB/s 3,000,000,000 375,000,000 Computer data interfaces SATA 3Gbit/s – Second generation
500 MB/s 4,000,000,000 500,000,000 Computer data interfaces PCI Express x1 v2.0
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
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

See also[edit]

Notes[edit]

  1. ^ Penn researchers calculate how much the eye tells the brain, 26 July 2006
  2. ^ "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. 
  3. ^ "Samsung overtakes". 

References[edit]