Bit rate vs baud rate?

It's basically the same. 9600 Baud is 9600 b/s. 9600 Baud/10 is likley characters per second. One of the useful indicators of the day. Serial ports.

In the RS232 context up to 3 bits are wasted.

START <data> <stop bits>

There is always 1 start bit.
there is 8 bits of data, 1 of those can be parity (error checking)
Then you have 1, 1.5 or 2 stop bits.

Why two stop bits. A motor can take a while to stop. The IBM selectric terminal had a baud rate of 134.5 As the speed went up, the number of stop bits settled at 1.

These encoders were motor driven and characters/s was a benchmark. The keyboard was actually designed to slow the human operator down.

Typically a 10 bit stream or 10 ASCII characters/s.

More data is used productively at protocals at higher bit rates.

For I2C, a lot of the data is used, so bit rate is more important.

then there is "Data Rate" and your sending packets around and there may be ways of correcting the data.

parity tells you something is wrong. A checksum is another level up. A CRC error might be able to be corrected.

A compiled program might have a checksum associated with the file. The file won't run unless the checksum calculated is the one stored in the file, but we have no idea where the error is.


Joined Aug 27, 2009
Baud rate refers to the number of signal or symbol changes that occur per second. The data bit rate could range from a fraction (Async) to a multiple (QAM) of that baud symbol rate depending on the encoding and modulation of the transmission media.

Serial 8N1 has an extra start and stop bit per 8 data bits, so the ratio is 10:1 so it takes 10 "bauds" to make 1 byte.


Joined Feb 24, 2006

Please, could you explain clearly difference between the bit and baud rate.
Bitrate refers to a system with exactly two symbols in the signaling alphabet. Baudrate refers to a generalized system where there can be an arbitrary number of symbols in the signaling alphabet. Clearly with more symbols in the signaling alphabet, the information content or bitrate can be much higher.