What Is Baud Rate?
Baud rate measures the number of signal changes (symbols) transmitted per second over a communication channel. It is named after Emile Baudot, a French telegraph engineer. In simple binary systems where each symbol carries one bit, baud rate equals bit rate. However, with advanced modulation schemes, each symbol can carry multiple bits, making the bit rate a multiple of the baud rate.
Serial communication protocols like UART, RS-232, and RS-485 use baud rate to configure the speed of data transmission. Common baud rates include 9600, 19200, 38400, 57600, and 115200. Each transmitted frame includes start bits, data bits, optional parity, and stop bits.
Baud Rate Formulas
Common Baud Rates
| Baud Rate | Bit Rate (Binary) | Common Use |
|---|---|---|
| 300 | 300 bps | Legacy modems |
| 9600 | 9,600 bps | Industrial devices, GPS |
| 19200 | 19,200 bps | PLC communication |
| 57600 | 57,600 bps | Bluetooth SPP |
| 115200 | 115,200 bps | Arduino, debug consoles |
| 921600 | 921,600 bps | High-speed serial |
Frequently Asked Questions
Is baud rate the same as bit rate?
Only for binary (NRZ) modulation where each symbol carries exactly one bit. With higher-order modulation like QPSK (2 bits/symbol) or 16-QAM (4 bits/symbol), the bit rate is a multiple of the baud rate.
What is the most common serial configuration?
The most common UART configuration is 8N1: 8 data bits, no parity, 1 stop bit, at 9600 or 115200 baud. This gives a frame size of 10 bits (1 start + 8 data + 1 stop) and an efficiency of 80%.
How does parity affect throughput?
Adding a parity bit increases the frame size by 1 bit, reducing the effective data throughput. For 8N1 configuration, efficiency is 80% (8/10). With parity (8E1), efficiency drops to about 72.7% (8/11). Parity provides basic single-bit error detection.