Megabit per second
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 | 10^{3} |
megabit per second | Mbit/s | 10^{6} |
gigabit per second | Gbit/s | 10^{9} |
terabit per second | Tbit/s | 10^{12} |
Binary prefixes (IEC 60027-2) | ||
kibibit per second | Kibit/s | 2^{10} |
mebibit per second | Mibit/s | 2^{20} |
gibibit per second | Gibit/s | 2^{30} |
tebibit per second | Tibit/s | 2^{40} |
Contents
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.
Variations
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 | 10^{3} | 10^{3}/8 |
kibibit per second | Kibit/s | 1,024 | 128 | 2^{10} | 2^{7} |
kilobyte per second | kB/s | 8,000 | 1,000 | 8x10^{3} | 10^{3} |
kibibyte per second | KiB/s | 8,192 | 1,024 | 2^{13} | 2^{10} |
megabit per second | Mbit/s | 1,000,000 | 125,000 | 10^{6} | 10^{6}/8 |
mebibit per second | Mibit/s | 1,048,576 | 131,072 | 2^{20} | 2^{17} |
megabyte per second | MB/s | 8,000,000 | 1,000,000 | 8x10^{6} | 10^{6} |
mebibyte per second | MiB/s | 8,388,608 | 1,048,576 | 2^{23} | 2^{20} |
gigabit per second | Gbit/s | 1,000,000,000 | 125,000,000 | 10^{9} | 10^{9}/8 |
gibibit per second | Gibit/s | 1,073,741,957 | 134,217,728 | 2^{30} | 2^{27} |
gigabyte per second | GB/s | 8,000,000,000 | 1,000,000,000 | 8x10^{9} | 10^{9} |
gibibyte per second | GiB/s | 8,589,934,592 | 1,073,741,824 | 2^{33} | 2^{30} |
terabit per second | Tbit/s | 1,000,000,000,000 | 125,000,000,000 | 10^{12} | 10^{12}/8 |
tebibit per second | Tibit/s | 1,099,511,627,776 | 137,438,953,472 | 2^{40} | 2^{37} |
terabyte per second | TB/s | 8,000,000,000,000 | 1,000,000,000,000 | 8x10^{12} | 10^{12} |
tebibyte per second | TiB/s | 8,796,093,022,208 | 1,099,511,627,776 | 2^{43} | 2^{40} |
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 | 10^{7} 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. 10^{7} 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
- Binary prefix
- Bit rate
- List of device bandwidths
- Orders of magnitude (bit rate)
- Orders of magnitude (data)
- SI prefix
Notes
References
- 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?"