Baud Rate Calculator
Divider, actual baud rate & error for microcontrollers
| Baudrate | Divisor (exact) | Divisor (rounded) | Actually (Bd) | Error % | Bitzeit (µs) | Byte Time 8N1 (µs) |
|---|---|---|---|---|---|---|
| 300 | 3333.3333 | 3333 | 300.03 | +0.01% | 3333 | 33330 |
| 1200 | 833.3333 | 833 | 1200.48 | +0.04% | 833 | 8330 |
| 2400 | 416.6667 | 417 | 2398.08 | -0.08% | 417 | 4170 |
| 4800 | 208.3333 | 208 | 4807.69 | +0.16% | 208 | 2080 |
| 9600 | 104.1667 | 104 | 9615.38 | +0.16% | 104 | 1040 |
| 19200 | 52.0833 | 52 | 19230.77 | +0.16% | 52 | 520 |
| 38400 | 26.0417 | 26 | 38461.54 | +0.16% | 26 | 260 |
| 57600 | 17.3611 | 17 | 58823.53 | +2.124% | 17 | 170 |
| 115200 | 8.6806 | 9 | 111111.11 | -3.549% | 9 | 90 |
| 230400 | 4.3403 | 4 | 250000 | +8.507% | 4 | 40 |
| 250000 | 4 | 4 | 250000 | 0% | 4 | 40 |
| 460800 | 2.1701 | 2 | 500000 | +8.507% | 2 | 20 |
| 500000 | 2 | 2 | 500000 | 0% | 2 | 20 |
| 921600 | 1.0851 | 1 | 1000000 | +8.507% | 1 | 10 |
| 1000000 | 1 | 1 | 1000000 | 0% | 1 | 10 |
| 2000000 | 0.5 | 1 | 1000000 | -50% | 1 | 10 |
Formula: Divisor = f_cpu / (Oversampling × Baudrate)
Calculate Accurate Serial Communication
The Baud Rate Calculator helps developers determine the precise timing for serial communication between microcontrollers and computers. By inputting your system's clock frequency and desired baud rate, the tool calculates the necessary divisor and identifies the actual baud rate achieved. It accounts for oversampling factors to provide an accurate error percentage. This ensures that data transmission remains stable and reliable by minimizing synchronization issues caused by imprecise timing in UART communication protocols.
Support for Popular Microcontrollers
To simplify configuration, the tool includes a wide range of popular microcontroller presets. You can quickly select configurations for devices like the ESP32, STM32F103 Blue Pill, Raspberry Pi Pico, and various Arduino models. Each preset automatically applies the correct clock frequency, allowing you to focus on finding the most stable baud rate for your specific hardware. This is essential for maintaining high-quality serial communication across different platforms.
Frequently asked questions
What does the error percentage mean in baud rate calculation?
The error percentage represents the difference between the target baud rate and the actual baud rate achievable with a specific clock frequency and divisor. A low error percentage, typically under 2%, is necessary for reliable serial communication to prevent data corruption during transmission between your microcontroller and other devices.
How do I choose the best baud rate for my project?
Choose a baud rate that balances speed with reliability based on your hardware's clock frequency. Use this tool to find a divisor that results in an error percentage as close to zero as possible. For most standard applications, 9600 or 115200 are common choices if the calculated error remains minimal.
Why is the divisor calculation important for UART?
The divisor determines how many clock cycles are used to represent a single bit of data. Because hardware clocks are rarely perfect multiples of standard baud rates, calculating the correct divisor ensures that the timing stays synchronized. This tool automates the calculation to provide both exact and rounded values for your code.