UART Baud Rate Calculator

Calculate UART baud rate, clock divider, actual baud rate and baud error.

UART Communication

MCU A
TX

→

UART

→

MCU B
RX

STEP 1

What do you want to calculate?

Baud Rate Calculate baud rate from clock and divider

Baud Divider Find the divider value

Clock Frequency Find required UART clock

Baud Error Compare desired and actual baud rate

STEP 2

Enter the values you know

UART Clock Frequency

Enter the clock supplied to the UART peripheral.

Baud Divider (USARTDIV / Prescaler)

The integer or fractional clock divisor used by the baud rate generator.

UART Oversampling

Use the oversampling value specified by your MCU UART peripheral.

Result

What is UART Baud Rate?

Baud rate defines how quickly UART communication transfers symbols per second. For typical NRZ binary UART configurations, one symbol represents one bit.

Basic UART Formula

Baud Rate = UART Clock ÷ (Oversampling × Divider)

Example

Suppose a microcontroller has a 16 MHz UART clock, uses 16x oversampling, and the divider is 8.6806.

Baud Rate = 16,000,000 ÷ (16 × 8.6806) ≈ 115200 baud

Common UART Baud Rates

1200 baud
2400 baud
4800 baud
9600 baud
19200 baud
38400 baud
57600 baud
115200 baud
230400 baud
460800 baud
921600 baud

Baud Rate Error Formula

Error % = ((Actual Baud - Desired Baud) ÷ Desired Baud) × 100

Standard UART tolerance typically allows up to ±2% to ±3% error before frame errors and bit misalignments occur.