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. It is sometimes mistakenly thought to mean 1,024 bits per second, using the binary meaning of the ''kilo-'' prefix, though this is incorrect.

Contents

Examples

Related units

'k' vs 'Ki'

'b' vs 'B'

Example usage

See also

Examples

★ 56k modem — 56,000 bit/s

★ 128 kbit/s mp3 — 128,000 bit/s [1]

★ 64k ISDN — 64,000 bit/s [2]

★ 1536k T1 — 1,536,000 bit/s (1.536 Mbit/s)
Most digital representations of audio are measured in kbit/s:
(These values vary depending on audio data compression schemes)

★ 4 kbit/s – minimum necessary for recognizable speech (using special-purpose speech codecs)

★ 8 kbit/s – telephone quality

★ 32 kbit/s – MW quality

★ 96 kbit/s – FM quality

★ 192 kbit/s – Nearly CD quality for a file compressed in the MP3 format

★ 1,411 kbit/s – CD audio (at 16-bits for each channel and 44.1 kHz)

Related units

'k' vs 'Ki'

'k' and 'Ki' stand for 'kilo' and kibi respectively. They are prefixes to units where 'k' stands for 1,000 and 'Ki' stands for 1,024, because 'Ki' comes from its use in computing where 2¹⁰ = 1,024. Unfortunately, 'K' is often incorrectly used instead of 'Ki'. Furthermore, the broad public not being necessarily aware of this subtle difference, usually 'Kbps' and 'kbps' indiscriminately, creating confusion. Whenever 'Kibps' is used, it is usually accurate.

'b' vs 'B'

'b' stands for 'bit' and 'B' stands for 'byte', where one byte refers to 8 bits. This can lead to confusion, as when a "1 Mega" connnection is advertised, it is in megabits, meaning the maximum achieveable download speed is actually 128 kilobyte per seconds.

Example usage

If the data rate of a data-stream 8,192 bits per second, then using the different capitalisations of letters this would be as follows:
8192 / 1000 = 8.192 kbps

8192 / 1024 = 8 Kbps

8192 / (8 x 1024) = 1 KBps

8192 / (8 x 1000) = 1.024 kBps

8192 / 8 = 1024 Bps
Bytes are typically used in modern systems, but even when 8-bit bytes are used, the number of kbyte/s is not necessarily exactly one eighth the number of kbit/s because the count of bytes might not include framing bits. For example, a 56 kbit/s RS-232 serial line transfers only 5.6 kbyte/s — not 7 kbyte/s — when used in the most common configuration (asynchronous, 8 data bits, no parity, one stop bit). It is fairly common to use kbyte/s with the binary meaning (1,024 byte/s) — more so than for kbit/s — perhaps because of the close relationship with the common binary usage of kilobyte for measuring file sizes.
Another related unit is the kibibit per second:
: 10³ = 1,000 bit/s = 1 'kbit/s' (one kilobit or one thousand bits per second)
: 2¹⁰ = 1,024 bit/s = 1 Kibit/s (one kibibit per second)
kbps is also commonly used for describing bit rates for streaming data such as video. The following table shows how much data would theoretically be downloaded when running such a stream in more common denotations.

kbps	50.00	150.00	139.81
KBps	6.10	18.31	17.07
MBpm	0.36	1.07	1.00
MBph	21.46	64.37	60.00

See also

★ kilobit/kibibit

★ kilobyte/kibibyte

★ Binary prefix