UART Baud Rate Error

Error% = |actual − target| / target × 100

Quick answer

This calculator solves Error% = |actual − target| / target × 100 for Baud Error. With Actual Baud Rate 1 kHz, Target Baud Rate 2.2 kHz, the result is 0.5455 %. It solves in 3 directions, so you can enter the values you have and get the one you need.

Calculator

Baud Error (%)
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Formula

Error% = |actual − target| / target × 100

Description

UART communication relies on both transmitter and receiver operating at the same baud rate within a tight tolerance. The baud rate error percentage quantifies how far the actual baud rate deviates from the target. Most UART peripherals derive their baud rate from a system clock using integer dividers, which often cannot produce the exact target frequency. Errors below 2% are generally acceptable for 8-bit frames, while errors above 3-5% typically cause framing errors and data corruption.

Variables

  • Error% — Percentage deviation from target baud rate
  • Actual — The baud rate actually achieved by the hardware (baud)
  • Target — The desired baud rate (baud)

Practical Notes

Common baud rates (9600, 115200, etc.) may not divide evenly from typical crystal frequencies. For example, a 16 MHz clock with a divide-by-16 UART achieves 115200 baud with 2.1% error. Using a 14.7456 MHz crystal gives exact division for all standard baud rates.

Symbols and units

Symbol Meaning Default unit Accepted units
error Baud Error % —, %
actual Actual Baud Rate Hz Hz, kHz, MHz, GHz
target Target Baud Rate Hz Hz, kHz, MHz, GHz

Step by step

  1. 1. What you know: Actual Baud Rate 1 kHz, Target Baud Rate 2.2 kHz
  2. 2. The relation: Error% = |actual − target| / target × 100
  3. 3. Substitute: actual = 1 kHz, target = 2.2 kHz
  4. 4. Result: Baud Error = 0.5455 %

Worked examples

Minimum range

Given: Actual Baud Rate 5 Hz, Target Baud Rate 11 Hz

Result: Baud Error = 0.5455 %

Low range

Given: Actual Baud Rate 50 Hz, Target Baud Rate 110 Hz

Result: Baud Error = 0.5455 %

Typical

Given: Actual Baud Rate 1 kHz, Target Baud Rate 2.2 kHz

Result: Baud Error = 0.5455 %

High range

Given: Actual Baud Rate 20 kHz, Target Baud Rate 44 kHz

Result: Baud Error = 0.5455 %

Maximum range

Given: Actual Baud Rate 0.2 MHz, Target Baud Rate 0.44 MHz

Result: Baud Error = 0.5455 %

Solving for each variable

Solve for Baud Error

Actual Baud Rate 5 Hz, Target Baud Rate 11 Hz → 0.5455 %

Solve for Actual Baud Rate

Baud Error 0.5 %, Target Baud Rate 11 Hz → 11.06 Hz

Solve for Target Baud Rate

Baud Error 0.5 %, Actual Baud Rate 5 Hz → 4.975 Hz

How Baud Error changes with Actual Baud Rate

Actual Baud Rate (input) Baud Error (result)
100 Hz 0.9545 %
0.25 kHz 0.8864 %
0.5 kHz 0.7727 %
0.75 kHz 0.6591 %
1 kHz 0.5455 %
1.5 kHz 31.82 %
2 kHz 9.091 %
4 kHz 0.8182 %
7 kHz 2.182 %
10 kHz 3.545 %

The same result in other units

Unit Value
% 0.5455
% 54.55

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Frequently asked questions

How do you calculate UART Baud Rate Error?

Use Error% = |actual − target| / target × 100. With Actual Baud Rate 1 kHz, Target Baud Rate 2.2 kHz, Baud Error works out to 0.5455 %.

What is the formula for UART Baud Rate Error?

The formula is Error% = |actual − target| / target × 100. UART communication relies on both transmitter and receiver operating at the same baud rate within a tight tolerance.

How do you find Actual Baud Rate when you know the other values?

Rearrange for Actual Baud Rate: with Baud Error 0.5 %, Target Baud Rate 11 Hz, Actual Baud Rate is 11.06 Hz.

How do you find Target Baud Rate when you know the other values?

Rearrange for Target Baud Rate: with Baud Error 0.5 %, Actual Baud Rate 5 Hz, Target Baud Rate is 4.975 Hz.

What units does UART Baud Rate Error use?

Baud Error is shown in %, %. Values are held in SI base units internally, so you can mix prefixes without converting by hand.

Related Concepts

All Communications formulas →
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