Bit rate

In telecommunications and computing, bit rate (sometimes written bitrate) is the speed at which bits are transmitted via radio or wire. It is also sometimes used interchangeably with baud rate, which is not in general the same.

It is usually expressed as bits per second, abbreviated bit/s, b/s, or informally bps. The b should always be lowercase, to avoid confusion with bytes per second (B/s), although this convention is often ignored.

Other SI prefixes are often used:

• 1000 b/s = 1 kb/s (one kilobit or one thousand bits per second)
• 1000 kb/s = 1 Mb/s (one megabit or one million bits per second)
• 1000 Mb/s = 1 Gb/s (one gigabit or one billion bits per second) ...

A similar convention unique to the computer industry, which uses the same prefixes (the k often erronously being capitalised), but a factor of 1024 = 2¹⁰, is less often used for bit rates, but almost always for amounts of bits and bytes. These different Binary prefixes and the capitalisation issue are constant reasons for confusion.

There are typically eight bits in a byte, but communications data rates are almost never expressed in bytes per second, with the notable exceptions of disk and memory I/O transfer rates. To convert from byte/s to bit/s, simply multiply by 8.

See also:

• Constant bit rate
• Variable bit rate
• Available bit rate

External links

• http://physics.nist.gov/cuu/Units/binary.html