LRC Checksum Calculator

Online LRC longitudinal redundancy check code calculator, supporting single and batch calculations, commonly used for Modbus ASCII communication data verification.

Bug report

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Speed and Stability: Processing speed depends on your device and browser. For large batch work, the desktop version may be more stable.

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If the online tool fails to load or run, try the desktop tool.https://tools.yikeaigc.com/

Tool Usage

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Set parameters, enter data, then generate the LRC result.

Supports HEX, ASCII, UTF-8 text, and raw byte input. Generates common Modbus ASCII two's-complement LRC and exports CSV or ZIP in batch.

Current mode Single

Processed 0

Success 0

Set calculation parameters

First confirm the input source and complement mode. For Modbus ASCII, usually choose HEX input, two's complement, and keep original byte order.

Save common settings first

Processing Method

Input format

Raw bytes are only for batch file mode.

Complement type

Byte order

LRC usually does not need byte order changes.

Output case

HEX separator

Ignore blank lines in batch text
Blank lines are not calculated. Trim each line
Good for pasted indented test data. Output full message with LRC
Append original bytes and LRC to the result. Auto-save when settings change
Restore common settings next time.

Enter data to check

In single mode, enter one message and click Calculate to view the LRC, sum, and full message.

HEX

Tip Please confirm the format on the Settings page first. HEX can be separated by spaces, commas, colons, or hyphens. Each two characters represent one byte.

Single data

Example: the standard two's complement LRC of 01 03 00 00 00 0A is F2.

Batch data, one per line

The preview shows the first 20 items. Copy and download include all results.

Choose files

All files will be processed. The UI shows only the first 20 files.

File preview

No files selected

Validation results

Results will appear here. For a single item, view steps; for batch data, copy or download.

Waiting to calculate

No results yet. Complete settings and input, then click Calculate.

Instructions

Software Usage Instructions

Set calculation parameters: First select single calculation, batch text, or batch file mode, then set the input format, complement type, byte order, and output format.
Select input format:
- Hexadecimal HEX: Enter data such as 01 03 00 00 00 0A, separated by spaces, commas, colons, or hyphens.
- ASCII characters: Calculate by character encoding, with each character corresponding to one byte.
- UTF-8 text: Suitable for byte checks of Chinese or multilingual text content.
- Raw file bytes: Calculate based on file byte content in batch file mode.
Configure complement method:
- Two's complement: A common LRC algorithm for Modbus ASCII. After summing, take the lower 8 bits, then invert and add 1.
- One's complement: After summing, take the lower 8 bits, then perform a bitwise inversion.
- Lower 8-bit sum: Outputs only the lower 8 bits of the sum, making it easier to compare algorithms from different devices.
Enter or select files: In single mode, enter one piece of data; in batch text mode, enter one piece of data per line; in batch file mode, you can select multiple TXT, CSV, HEX, BIN, or DAT files.
Start calculation: Click “Calculate and View Results”, and the tool will display the LRC check value, sum, LRC ASCII, complete message, and calculation process.
Copy and download: Single results can be copied or downloaded as CSV; batch text can be exported as CSV; batch files generate result files based on the original file names, and multiple files are packaged as a ZIP.
Save settings: Commonly used input formats, complement methods, and output styles can be saved and reused next time.

FAQ

A: The common LRC algorithm first sums all data bytes, keeps the lower 8 bits, and then takes the two's complement, which means inverting the bits and adding 1. Modbus ASCII messages usually use this calculation method.

A: No. LRC is usually calculated only for the bytes corresponding to the address, function code, and data fields. It does not include the starting colon or the trailing carriage return and line feed.

A: HEX input requires every two characters to represent one byte, for example 01 03 00 00. You can separate them with spaces, commas, colons, or hyphens, or use no separators.

A: Two's complement inverts the low 8 bits of the accumulated sum and adds 1, making it suitable for Modbus ASCII; one's complement only inverts without adding 1; low 8-bit sum does not take the complement, making it easier to verify special checksum rules in device documentation.

A: The result file will keep the original file name and append an LRC result identifier. If a duplicate name is encountered, a numeric suffix will be added automatically to distinguish it, and multiple result files will be packaged into a ZIP for download.

A: LRC is mainly performed through byte accumulation and complement operations, and is commonly used in Modbus ASCII; CRC uses polynomial operations and is common in Modbus RTU. They differ in applicable protocols and calculation processes.