Data rate units

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Bit rates
NameSymbolMultiple
Decimal prefixes (SI)
kilobit per secondkbit/s103
megabit per secondMbit/s106
gigabit per secondGbit/s109
terabit per secondTbit/s1012
Binary prefixes (IEC 80000-13)
kibibit per secondKibit/s210
mebibit per secondMibit/s220
gibibit per secondGibit/s230
tebibit per secondTibit/s240
 
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Bit rates
NameSymbolMultiple
Decimal prefixes (SI)
kilobit per secondkbit/s103
megabit per secondMbit/s106
gigabit per secondGbit/s109
terabit per secondTbit/s1012
Binary prefixes (IEC 80000-13)
kibibit per secondKibit/s210
mebibit per secondMibit/s220
gibibit per secondGibit/s230
tebibit per secondTibit/s240

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):

UnitBitsBits / 1,000,000
Mega-bit1,000,0001.0
Mebi-bit1,048,5761.05
Mega-byte8,000,0008.0
Mebi-byte8,388,6088.39

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:

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:

Gigabit per second[edit]

A gigabit per secondGbit/s, Gbps, or Gb/s – is a unit of data transfer rate equal to:

Terabit per second[edit]

A terabit per secondTbit/s, Tbps, or Tb/s – is a unit of data transfer rate equal to:

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:

Mebibit per second[edit]

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

Gibibit per second[edit]

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

Tebibit per second[edit]

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

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:

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:

Gigabyte per second[edit]

A gigabyte per secondGBps or GB/s – is a unit of data transfer rate equal to:

Terabyte per second[edit]

A terabyte per secondTBps or TB/s – is a unit of data transfer rate equal to:

Binary multiples of bytes[edit]

Kibibyte per second[edit]

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

Mebibyte per second[edit]

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

Gibibyte per second[edit]

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

Tebibyte per second[edit]

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

Conversion table[edit]

NameSymbolbit per secondbyte per secondbit per second (formula)byte per second (formula)
bit per secondbit/s10.12511/8
byte per secondB/s8181
kilobit per secondkbit/s1,000125103103/8
kibibit per secondKibit/s1,02412821027
kilobyte per secondkB/s8,0001,0008x103103
kibibyte per secondKiB/s8,1921,024213210
megabit per secondMbit/s1,000,000125,000106106/8
mebibit per secondMibit/s1,048,576131,072220217
megabyte per secondMB/s8,000,0001,000,0008x106106
mebibyte per secondMiB/s8,388,6081,048,576223220
gigabit per secondGbit/s1,000,000,000125,000,000109109/8
gibibit per secondGibit/s1,073,741,957134,217,728230227
gigabyte per secondGB/s8,000,000,0001,000,000,0008x109109
gibibyte per secondGiB/s8,589,934,5921,073,741,824233230
terabit per secondTbit/s1,000,000,000,000125,000,000,00010121012/8
tebibit per secondTibit/s1,099,511,627,776137,438,953,472240237
terabyte per secondTB/s8,000,000,000,0001,000,000,000,0008x10121012
tebibyte per secondTiB/s8,796,093,022,2081,099,511,627,776243240

Examples of bit rates[edit]

QuantityUnitbits per secondbytes per secondFieldDescription
56kbit/s56,0007,000Networking56kbit modem – 56 kbit/s – 56,000 bit/s
64kbit/s64,0008,000Networking64kbit/s in an ISDN B channel or best quality, uncompressed telephone line.
1,536kbit/s1,536,000192,000Networking24 channels of telephone in the US, or a good VTC T1.
10Mbit/s10,000,0001,250,000Networking107 bit/s is the speed of classic Ethernet: 10BASE2, 10BASE5, 10BASE-T
10Mbit/s10,000,0001,250,000BiologyResearch suggests that the human retina transmits data to the brain at the rate of ca. 107 bit/sec[1]
1Gbit/s1,000,000,000125,000,000NetworkingGigabit Ethernet
10Gbit/s10,000,000,0001,250,000,000Networking10 Gigabit Ethernet
1Tbit/s1,000,000,000,000125,000,000,000NetworkingSEA-ME-WE 4 submarine communications cable – 1.28 terabits per second[2]
4kbit/s4,000500Audio dataminimum achieved for encoding recognizable speech (using special-purpose speech codecs)
8kbit/s8,0001,000Audio datalow bit rate telephone quality
32kbit/s32,0004,000Audio dataMW quality and ADPCM voice in telephony, doubling the capacity of a 30 chan link to 60 ch.
128kbit/s128,00016,000Audio data128 kbit/s MP3 – 128,000 bit/s
192kbit/s192,00024,000Audio data192 kbit/s MP3 – 192,000 bit/s
1,411.2kbit/s1,411,200176,400Audio dataCD audio (uncompressed, 16 bit samples × 44.1 kHz × 2 channels)
2Mbit/s2,000,000250,000Video data30 channels of telephone audio or a Video Tele-Conference at VHS quality
8Mbit/s8,000,0001,000,000Video dataDVD quality
27Mbit/s27,000,0003,375,000Video dataHDTV quality
1.244Gbit/s1,244,000,000155,500,000NetworkingOC-24, a 1.244 Gbit/s SONET data channel
9.953Gbit/s9,953,000,0001,244,125,000NetworkingOC-192, a 9.953 Gbit/s SONET data channel
39.813Gbit/s39,813,000,0004,976,625,000NetworkingOC-768, a 39.813 Gbit/s SONET data channel, the fastest in current use
60MB/s480,000,00060,000,000Computer data interfacesUSB 2.0 High-Speed
625MB/s5,000,000,000625,000,000Computer data interfacesUSB 3.0 SuperSpeed
98.3MB/s786,432,00098,304,000Computer data interfacesFireWire IEEE 1394b-2002 S800
120MB/s960,000,000120,000,000Computer data interfacesHarddrive read, Samsung SpinPoint F1 HD103Uj[3]
133MB/s1,064,000,000133,000,000Computer data interfacesParallel ATA UDMA 6
133MB/s1,064,000,000133,000,000Computer data interfacesPCI 32-bit at 33 MHz (standard configuration)
188MB/s1,504,000,000188,000,000Computer data interfacesSATA 1.5Gbit/s – First generation
375MB/s3,000,000,000375,000,000Computer data interfacesSATA 3Gbit/s – Second generation
500MB/s4,000,000,000500,000,000Computer data interfacesPCI Express x1 v2.0
750MB/s6,000,000,000750,000,000Computer data interfacesSATA 6Gbit/s – Third generation
1067MB/s5,533,333,3331,066,666,667Computer data interfacesPCI-X 64 bit 133 MHz
1250MB/s10,000,000,0001,250,000,000Computer data interfacesThunderbolt
2500MB/s20,000,000,0002,500,000,000Computer data interfacesThunderbolt 2
8000MB/s64,000,000,0008,000,000,000Computer data interfacesPCI Express x16 v2.0
12000MB/s96,000,000,00012,000,000,000Computer data interfacesInfiniBand 12X QDR
16000MB/s128,000,000,00016,000,000,000Computer data interfacesPCI 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]