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UART Baud Rate Calculator
Calculate UART divisor, actual baud rate, baud error, and compatibility status from clock frequency, target baud rate, oversampling, and fractional divider resolution.
Input Parameters
Results
UART tolerance is shared between transmitter and receiver. A low local error gives more margin for the other side, clock drift, and temperature variation.
Equations Used
Ideal divider: Divider = UART clock / (Oversampling × Target baud)
Actual baud: Actual baud = UART clock / (Oversampling × Programmed divider)
Baud error: Error % = (Actual - Target) / Target × 100%
Frequently Asked Questions (FAQ)
Q1: What does a UART baud rate calculator do?
It calculates the actual baud rate and error produced by a clock and UART divider setting.
Q2: What baud error is acceptable?
Many UART links tolerate around ±2% total error, but the real limit depends on frame length, oversampling, and the receiver.
Q3: Why does MCU clock frequency matter?
The UART baud generator divides the peripheral clock, so not every clock can produce every baud rate exactly.
Q4: Why use fractional dividers?
Fractional dividers reduce baud error by allowing finer divisor steps than integer-only hardware.
Q5: Is 115200 baud always accurate?
No. The actual error depends on clock frequency, oscillator accuracy, divider resolution, and peripheral implementation.
