Tools
UART Baud Rate Calculator
Enter your MCU clock and desired baud rate to compute the actual baud rate, register divisor, and error percentage for 16× and 8× oversampling modes.
Results for 115,200 baud @ 16 MHz
16× oversampling
Standard mode (STM32 OVER8=0, AVR normal)
Register divisor (BRR)9
Actual baud rate111,111 bps
Error-3.549%
Tolerance✗ Exceeds 2%
8× oversampling
High-speed mode (STM32 OVER8=1, AVR U2X=1)
Register divisor (BRR)17
Actual baud rate117,647 bps
Error+2.124%
Tolerance✗ Exceeds 2%
All Common Baud Rates @ 16 MHz
| Baud | 16× BRR | 16× Error | 8× BRR | 8× Error |
|---|---|---|---|---|
| 1,200 | 833 | +0.04% | 1667 | -0.02% |
| 2,400 | 417 | -0.08% | 833 | +0.04% |
| 4,800 | 208 | +0.16% | 417 | -0.08% |
| 9,600 | 104 | +0.16% | 208 | +0.16% |
| 19,200 | 52 | +0.16% | 104 | +0.16% |
| 38,400 | 26 | +0.16% | 52 | +0.16% |
| 57,600 | 17 | +2.12% | 35 | -0.79% |
| 115,200 | 9 | -3.55% | 17 | +2.12% |
| 230,400 | 4 | +8.51% | 9 | -3.55% |
| 460,800 | 2 | +8.51% | 4 | +8.51% |
| 921,600 | 1 | +8.51% | 2 | +8.51% |
Green = ≤2% error (standard tolerance) · Amber = 2–5% · Red = >5%