What is the difference between baud rate and bit rate?

Bit rate:- Bit rate is nothing but number of bits transmitted per second.For example if Bit rate is 1000bps then 1000 bits are i.e. 0s or 1s transmitted per second.

Baud rate:- It means number of time signal changes its state.When the signal is binary then baud rate and bit rate are same.

bit rate : no of bits(0 or 1 for binary signal) transmitted per second.

baud rate : no of symbols per second.

A symbol consists of 'n' number of bits.

Baud rate = (bit rate)/n

So baud rate is always less than or equal to bit rate.It is equal when signal is binary.

Bit per second is what is means - rate of data transmission of ones and zeros per second are used.This is called bit per second(bit/s. However, it should not be confused with bytes per second, abbreviated as bytes/s, Bps, or B/s.

Raw throughput values are normally given in bits per second, but many software applications report transfer rates in bytes per second.

So, the standard unit for bit throughput is the bit per second, which is commonly abbreviated bit/s, bps, or b/s.

Baud is a unit of measure of changes , or transitions , that occurs in a signal in each second.

For example if the signal changes from one value to a zero value(or vice versa) one hundred times per second, that is a rate of 100 baud.

The other one measures data(the throughput of channel), and the other ones measures transitions(called signalling rates).

For example if you look at modern modems they use advanced modulation techniques that encoded more than one bit of data into each transition.

Thanks.

This topic is confusing because there are 3 terms in use when people think there are just 2, namely:

"bit rate": units are bits per second

"baud": units are symbols per second

"Baud rate": units are bits per second

"Baud rate" is really a marketing term rather than an engineering term. "Baud rate" was used by modem manufactures in a similar way to megapixels is used for digital cameras. So the higher the "Baud rate" the better the modem was perceived to be.

The engineering unit "baud" is already a rate (symbols per second) which distinguishes it from the "Baud rate" term. However, you can see from the answers that people are confusing these 2 terms together such as baud/sec which is wrong.

From an engineering point of view, I recommend people use the term "bit rate" for "RS-232" and consign to history the term "Baud rate". Use the term "baud" for modulation schemes but avoid it for "RS-232".

In other words, "bit rate" and "Baud rate" are the same thing which means how many bits are transmitted along a wire in one second. Note that bits per second (bps) is the low-level line rate and not the information data rate because asynchronous "RS-232" has start and stop bits that frame the 8 data bits of information so bps includes all bits transmitted.

Replies here are misleading. Saying true, but no one tell that for UART a symbol is not a single character but a single bit and this way the question was tagged.

For example 115200/8n1 is 11520 bytes per second as a single ASCII character is a 1 start bit plus 8 data bit plus 1 stop bit.

As correctly pointed out in the other replies, the bitrate is the amount of logical (or "abstract high level") information transferred in a given time, while baud rate is the number of symbols (more or less "signal changes") in the physical line in a given time.

While it is easy to understand that if a transmitted symbol carries 4 bits of information, then the bitrate is four time the baud rate, things get blurred in case of, for example, a RS-232 serial line.

The classic serial line works on bytes (well, "frames"), not bits. There is no way to transmit fewer that 8 bits (i.e. a byte), because the serial line defines a "frame" (I assume frames with 8 data bits, no parity, 1 start bit and 1 stop bit); and this is usually OK, because devices (computers) work probably on bytes, not single bits.

Given that, when a device sends a byte, i.e. 8 bits, the physical lines transmits 10 symbols, because to the original data composed of 8 bits, 2 more are added (start and stop bits, they are needed for synchronization). Some confusion can arise because the symbols transmitted on the physical line are also called "bits", but they are really symbols (MARK and SPACE, actually).

So in that classic RS-232 (in case of "8N1" frame) the bitrate is actually 8/10 of the baudrate. If we add the parity bit, the ratio lowers further and becomes 8/11.

The number of bits or symbols per second translates directly to the duration of them (bits or symbols). What does it mean for an engineer designing a system? It means that if he is designing a line filter to protect the line or reduce the noise, he should take the duration (or frequency) of the symbols transmitted on that line. For a baudrate of 1000 baud, he knows that the frequency of the signal is 1 KHz, and that a symbol has a duration of 1 ms. Fine. But if he has to calculate how much time is needed to transfer a file from a device to another, say a file of 1000 bytes, he must consider the bitrate, not the baudrate! Because the devices, at higher level, do not even see the start and stop bits, they are only a burden which slow down the communication (but they are useful for error checking).

To take it to the extreme case, imagine that a serial frame is just a bit long. For every bit transmitted by a device, three symbols would travel in the physical line. And if a parity were added, then four symbol would travel: the bitrate would be 1/4 of the baudrate. And if we add a second stop bit, the bitrate goes down to 1/5 of the baudrate!