What is the difference between baud rate and bit rate?

Baud rate is the number of symbol changes per second. Bit rate (bps) is the number of bits per second. They are equal only when each symbol carries exactly 1 bit (binary signaling). With multi-level modulation — such as QPSK (2 bits/symbol) or 16-QAM (4 bits/symbol) — bit rate = baud rate × bits per symbol.

Why is UART throughput lower than the baud rate suggests?

Standard UART adds framing bits around each byte. An 8N1 frame (8 data bits, no parity, 1 stop bit) uses 10 line bits to send 8 data bits, so effective throughput is 80% of the gross bit rate. Adding parity or a second stop bit increases overhead further.

What does 8N1 mean for RS-232?

"8N1" means 8 data bits, No parity, 1 stop bit — plus the mandatory 1 start bit. This is the most common UART configuration. The total frame is 10 bits, carrying 8 bits of data.

Does SPI have framing overhead like UART?

SPI has no start/stop bits or parity — data is clocked synchronously, so every bit on the bus is a data bit. Effective bit rate equals the clock frequency. Overhead comes from chip-select assertion time and inter-byte gaps at the software level, not the protocol itself.

What baud rates are standard for serial ports?

Common standard baud rates are 1200, 2400, 4800, 9600, 19200, 38400, 57600, 115200, 230400, 460800, and 921600. Many modern microcontrollers also support non-standard rates by programming a clock divider directly.

Can I use this for RF or modem calculations?

Yes. The baud-to-bit-rate conversion applies to any modulation scheme. For example, a 2400 baud modem using 16-QAM (4 bits/symbol) achieves 9600 bps. The serial throughput tab is specific to UART-style framing.

Baud Rate to Bit Rate Calculator

Name: Baud Rate to Bit Rate Calculator
Availability: InStock
Author: Nham Vu

Enter a baud rate and bits-per-symbol (modulation) to get the bit rate, or enter a bit rate to find the required baud rate. Also estimates real data throughput for UART, RS-232, and SPI.

Conversion Direction

Baud Rate (Bd)

Bits per Symbol

Common Presets

Baud Rate / Bit Rate Conversion

Baud Rate

9,600

symbols / second

Bit Rate

9,600

bits / second

Bits per Symbol

Bit Rate (readable)

9.6 Kbps

Serial Protocol Throughput

Gross Bit Rate

115,200

bps (line speed)

Data Throughput

11,520

bytes / second

Overhead

20.0%

Efficiency

80.0%

kB/s

11.25

Transfer Time Estimates

Payload Size	Time

Key Relationship

Bit Rate = Baud Rate × Bits per Symbol

For binary serial links (UART, RS-232, RS-485, SPI), bits per symbol = 1, so baud rate equals bit rate. For RF modulations like 16-QAM, a 2400 Bd channel carries 9600 bps.

Summary

Enter a baud rate and bits-per-symbol (modulation) to get the bit rate, or enter a bit rate to find the required baud rate. Also estimates real data throughput for UART, RS-232, and SPI.

How it works

Choose a conversion direction: Baud to Bit Rate or Bit Rate to Baud.
Enter the baud rate (or bit rate) value.
Select the bits per symbol for your modulation: 1 (NRZ/OOK), 2 (4-QAM/QPSK), 3 (8-QAM), 4 (16-QAM), 6 (64-QAM), or 8 (256-QAM).
Read the converted value and gross bit rate instantly.
Switch to the Serial Throughput tab to calculate effective data rate for UART, RS-232, RS-485, or SPI after framing overhead.
For UART/RS-232/RS-485, set data bits, stop bits, and parity to see how many bytes per second actually carry payload.

Use cases

Verify that a 9600 baud RS-232 link delivers only 960 bytes/s of payload with standard 8N1 framing.
Determine the baud rate needed on a QPSK radio link to achieve a target bit rate.
Compare throughput of UART configurations (7E1 vs 8N1 vs 8N2) at the same baud rate.
Calculate how many sensors can share an RS-485 bus at a given polling rate.
Check whether a 115200 baud serial debug port is fast enough to stream sensor data in real time.
Teach the difference between baud rate and bit rate when explaining modulation schemes.

Frequently Asked Questions

Last updated: 2026-07-01 · Reviewed by Nham Vu