Baud Rate Calculator Formula

Understand the math behind the baud rate calculator. Each variable explained with a worked example.

Use the Baud Rate Calculator

Formulas Used

Gross Bit Rate

gross_bit_rate = baud_rate * bits_per_symbol

Effective Data Rate

effective_throughput = baud_rate * bits_per_symbol * data_bits_per_frame / (data_bits_per_frame + start_stop_bits)

Protocol Efficiency

efficiency_pct = data_bits_per_frame / (data_bits_per_frame + start_stop_bits) * 100

Variables

VariableDescriptionDefault
baud_rateBaud Rate (symbols/s)(Bd)9600
bits_per_symbolBits per Symbol(bits)1
start_stop_bitsOverhead Bits per Frame(bits)2
data_bits_per_frameData Bits per Frame(bits)8

How It Works

Baud Rate vs Bit Rate

Formulas

Bit Rate = Baud Rate x Bits per Symbol

Throughput = Bit Rate x Data Bits / (Data + Overhead Bits)

UART at 9600 baud with 8N1 framing: 9600 bps gross, 7680 bps effective (80% efficient due to start/stop bits).

Worked Example

UART at 9600 baud, 1 bit/symbol, 8 data bits, 2 overhead bits (start + stop).

baud_rate = 9600bits_per_symbol = 1start_stop_bits = 2data_bits_per_frame = 8
  1. 01Gross bit rate = 9600 x 1 = 9600 bps
  2. 02Effective = 9600 x 8 / 10 = 7680 bps
  3. 03Efficiency = 8 / 10 = 80%

Frequently Asked Questions

What is the difference between baud and bps?

Baud is symbols per second. Bps is bits per second. They are equal only when each symbol carries one bit (e.g., basic UART).

How can bit rate exceed baud rate?

With multi-level modulation (QAM, PSK) each symbol encodes multiple bits. QAM-256 sends 8 bits per symbol.

Common UART baud rates?

9600, 19200, 38400, 57600, 115200. Higher rates require shorter cables or better line drivers.

Ready to run the numbers?

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