Data rate units
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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 units bit per second or byte per second.
| Bit rates | ||
|---|---|---|
| Decimal prefixes (SI) | ||
| Name | Symbol | Multiple |
| 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 |
Contents |
[edit] Avoiding confusion
- See also Bit rate for the differences of gross and net bitrate, throughput and goodput.
To be as explicit as possible, both the prefix and the suffix of the unit must be known. For example, the abbreviation 2-MB can actually be expanded in 4 different ways ("mega-" vs "mebi-" and "-bit" vs "-byte"). The difference in the associated numbers can be immense:
| 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 approximately 5% difference between the corresponding mega- and mebi- units with an 700% difference between -bit and -byte units. Explicitness in units is important because different interpretations can mean up to an 740% difference in the amount of data considered within one unit (the difference can become even larger across different prefix units).
[edit] Prefix: k vs. Ki
'k' stands for kilo, meaning 1,000, while 'Ki' stands for kibi, meaning 1,024. The standardized binary prefixes such as kibi were relatively recently introduced and still face low adoption. 'K' and 'k' are often used to mean 1,024, especially in KB, the kilobyte.
[edit] Suffix: b vs. B
'b' stands for 'bit' and 'B' stands for 'byte'. However, it has been suggested that 'bit' should not be abbreviated since the difference between bit and byte can lead to confusion. In the context of data rate units, one byte refers to 8 bits. For example, when a "1 Mbps" connection is advertised, it usually means that the maximum achievable download bandwidth is 1 megabit/s (million bits per second), which is actually 0.125 MB/s (megabyte per second), or about 0.1192 MiB/s (mebibyte per second).
Often it is assumed that there are TEN (10, not 8) bits per byte.[who?] Each 8 bits may have about two extra checksum-type bits, making ten bits in actual use.[citation needed] So "256 b/s" will be less than "256 B/s", not the opposite from what we might expect.
[edit] Decimal multiples of bits
[edit] Kilobit per second
A kilobit per second (kbit/s or kb/s or kbps) is a unit of data transfer rate equal to:
- 1,000 bits per second or
- 125 bytes per second.
[edit] Megabit per second
A megabit per second (Mbit/s or Mb/s or Mbps) is a unit of data transfer rate equal to:
- 1,000,000 bits per second or
- 1,024 kilobit per second|kilobits per second]] or
- 125,000 bytes per second.
[edit] Gigabit per second
A gigabit per second (Gbit/s or Gb/s or Gbps) is a unit of data transfer rate equal to:
- 1,000 megabits per second or
[edit] Terabit per second
A terabit per second (Tbit/s or Tb/s or Tbps) is a unit of data transfer rate equal to:
- 1,000,000,000,000 bits per second
- 1,000,000,000 kilobits per second or
- 1,000,000 megabits per second or
- 1,000 gigabits per second or
- 125,000,000,000 bytes per second.
[edit] Binary multiples of bits
[edit] 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. The word "kibibit" is not capitalized, but the abbreviation "Kibit" is.
[edit] 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.
[edit] 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.* 1,024 mebibits per second.* 1,024 mebibits per second.
[edit] 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 or
- 1,048,576 mebibits per second or
- 1,024 gibibits per second.
[edit] Decimal multiples of bytes
[edit] Kilobyte per second
A kilobyte per second (kB/s or kBps) 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.
[edit] Megabyte per second
A megabyte per second (MB/s or MBps) 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.
[edit] Gigabyte per second
A gigabyte per second (GB/s or GBps) 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.
[edit] Terabyte per second
A terabyte per second (TB/s or TBps) 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.
[edit] Binary multiples of bytes
[edit] Kibibyte per second
A kibibyte per second (KiB/s or KiBps) is a unit of data transfer rate equal to:
- 1,024 bytes per second, or
- 8 kibibits per second, or
- 8192 bits per second.
[edit] Mebibyte per second
A mebibyte per second (MiB/s or MiBps) 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.
[edit] Gibibyte per second
A gibibyte per second (GiB/s or GiBps) 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.
[edit] Tebibyte per second
A tebibyte per second (TiB/s or TiBps) 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.
- 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.
[edit] Conversion formulas
| 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 | 8*10^3 | 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 | 8*10^6 | 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 | 1,073,741,824 | 134,217,728 | 2^30 | 2^27 |
| gigabyte per second | GB/s | 8,000,000,000 | 1,000,000,000 | 8*10^9 | 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 | 8*10^12 | 10^12 |
| tebibyte per second | TiB/s | 8,796,093,022,208 | 1,099,511,627,776 | 2^43 | 2^40 |
[edit] Examples
| Quantity | Unit | bits per second | bytes per second | Field | Description |
|---|---|---|---|---|---|
| 56 | kbit/s | 56,000 | 7,000 | Networking | 56k modem – 56 kb/s – 56,000 b/s |
| 64 | kbit/s | 64,000 | 8,000 | Networking | 64k ISDN – 64 kb/s – 64,000 b/s |
| 1536 | kbit/s | 1,536,000 | 192,000 | Networking | 1536k T1 – 1,536,000 b/s (1.536 Mb/s) |
| 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 cable – 1.28 terabits per second [1] |
| 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 | telephone quality |
| 32 | kbit/s | 32,000 | 4,000 | Audio data | MW quality |
| 128 | kbit/s | 128,000 | 16,000 | Audio data | 128 kb/s MP3 – 128,000 b/s |
| 192 | kbit/s | 192,000 | 24,000 | Audio data | Nearly CD quality for a file compressed in the MP3 format |
| 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 | 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 Gb/s SONET data channel |
| 9.953 | Gbit/s | 9,953,000,000 | 1,244,125,000 | Networking | OC-192, a 9.953 Gb/s SONET data channel |
| 39.813 | Gbit/s | 39,813,000,000 | 4,976,625,000 | Networking | OC-768, a 39.813 Gb/s SONET data channel, the fastest in current use |
| 60 | MB/s | 480,000,000 | 60,000,000 | Computer data interfaces | USB 2.0 |
| 625 | MB/s | 5,000,000,000 | 625,000,000 | Computer data interfaces | USB 3.0 |
| 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 [1] |
| 133 | MB/s | 1,064,000,000 | 133,000,000 | Computer data interfaces | PATA 33 – 133 MB/s |
| 150 | MB/s | 1,200,000,000 | 150,000,000 | Computer data interfaces | SATA 1.5Gb/s – First generation |
| 300 | MB/s | 2,400,000,000 | 300,000,000 | Computer data interfaces | SATA 3Gb/s – Second generation |
| 600 | MB/s | 4,800,000,000 | 600,000,000 | Computer data interfaces | SATA 6Gb/s – Third generation |
| 533 | MB/s | 4,264,000,000 | 533,000,000 | Computer data interfaces | PCI 133 – 533 MB/s |
[edit] See also
[edit] Notes
- ^ "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. http://web.archive.org/web/20070317223056/http://www.fujitsu.com/global/news/pr/archives/month/2005/20051213-01.html. Retrieved 2008-01-31.
[edit] 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+
