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Bitrate

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. Note that "speed" in this context doesn't refer to distance/time but to "quantity of information"/time, and thus should be distinguished from the "propagation speed" (which depends on the transmission medium and has the usual physical meaning).

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.

SI prefixes are often used:

• 1000 bit/s = 1 kbit/s (one kilobit or one thousand bits per second)
• 1000 kbit/s = 1 Mbit/s (one megabit or one million bits per second)
• 1000 Mbit/s = 1 Gbit/s (one gigabit or one billion bits per second)
• ...

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

There are typically eight bits in a byte (octet), 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.

In audio and audiovisual files quality is often measured in bitrate. The bitrate shows how large the quantity of the stored bits per second of data is.

Example for audio formats:

See also

• Constant bit rate
• Variable bit rate