In telecommunications, data transfer rate is the average number of bits, characters
or symbols, or blocks per unit time passing between equipment in a data transmission system.
Most commonly, measurements of data transfer rate are reported in multiples of unit bits
per second or occasionally in bytes per second. The data rates of modern residential high-speed
Internet connections are most commonly expressed in multiples of bits per second, such as megabits
per second.
Standards for unit symbols and prefixes
Unit symbol The ISQ symbols for the bit and byte are bit
and B. In the context of data rate units, one byte consists of 8 bits, and is synonymous
with the unit octet. The abbreviation bps is often used to mean bit/s, so that when
a 1 Mbps connection is advertised, it usually means that the maximum achievable bandwidth
is 1 Mbit/s, which is 0.125 MB/s, or about 0.1192 MiB/s. The IEEE uses the symbol b
for bit. Prefix
In both the SI and ISQ, the prefix k stands for kilo, meaning 1000, while Ki is the symbol
for the binary prefix kibi-, meaning 1024. The binary prefixes were introduced in 1998
by the International Electrotechnical Commission and in IEEE 1541-2002 which was reaffirmed
on 27 March 2008. The letter K is often used as a non-standard abbreviation for 1024, especially
in "KB" to mean KiB, the kilobyte in its binary sense.
Variations In 1999, the 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.
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
kilobit per second is a unit of data transfer rate equal to:
1000 bits per second 125 bytes per second
Gigabit per second gigabit per second 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
terabit per second 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
The prefix name for binary prefixes is not capitalized, but the prefix symbol is.
Kibibit per second The kibibit per second is a unit of data transfer
rate equal to: 1024 bits per second
Mebibit per second The mebibit per second is a unit of data transfer
rate equal to: 1,048,576 bits per second
1,024 kibibits per second Gibibit per second
The gibibit per second 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
The tebibit per second 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 These units are often not used in the suggested
ways! See above section titled "variations". Kilobyte per second
kilobyte per second 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
megabyte 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 gigabyte per second 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 terabyte per second 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
Kibibyte per second The kibibyte per second 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 The mebibyte per second 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 The gibibyte per second 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 The tebibyte per second 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 Examples of bit rates
See also Binary prefix
Bit rate List of device bandwidths
Orders of magnitude Orders of magnitude
SI prefix Notes
References International Electrotechnical Commission.
"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?"