What is the formula for CRC / LRC / Checksum Calculator?

Core formula: CRC-16/MODBUS: init FFFF, reflected polynomial A001, low byte first. The tool returns results instantly using this formula and the selected parameters.

CRC / LRC / Checksum Calculator

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Paste a hex frame and get CRC16 (MODBUS / CCITT / XMODEM / IBM), CRC8, CRC32, LRC, XOR and sum checks, with the checksum bytes appended to the frame.

Key points

CRC / LRC / Checksum Calculator: Paste a hex frame and get CRC16 (MODBUS / CCITT / XMODEM / IBM), CRC8, CRC32, LRC, XOR and sum checks, with the checksum bytes appended to the frame. Formula: CRC-16/MODBUS: init FFFF, reflected polynomial A001, low byte first. Enter parameters on the DD-CAT IDE online tool page to get results instantly, with a calculation-model diagram that updates with the inputs. A CRC is defined by four parameters: polynomial, init, reflection and final XOR — the same "CRC16" name gives different results. MODBUS RTU sends the CRC low byte first — do not confuse display order with transmission order.

Inputs

CRC-16/MODBUS: init FFFF, reflected polynomial A001, low byte first

Calculation model (updates with parameters)

Data bytes	6
CRC-16/MODBUS (low byte first) 结果	C5 CD
Result (decimal)	50637	Read big-endian, for cross-checking only
Checksum bytes	2 字knot (low byte first)
Full frame with checksum	01 03 00 00 00 0A C5 CD	Paste straight into a serial terminal

Engineering notes

A CRC is defined by four parameters: polynomial, init, reflection and final XOR — the same "CRC16" name gives different results.
MODBUS RTU sends the CRC low byte first — do not confuse display order with transmission order.

FAQ

What is CRC / LRC / Checksum Calculator for?: Paste a hex frame and get CRC16 (MODBUS / CCITT / XMODEM / IBM), CRC8, CRC32, LRC, XOR and sum checks, with the checksum bytes appended to the frame.
What is the formula for CRC / LRC / Checksum Calculator?: Core formula: CRC-16/MODBUS: init FFFF, reflected polynomial A001, low byte first. The tool returns results instantly using this formula and the selected parameters.
What engineering notes should I keep in mind when using CRC / LRC / Checksum Calculator?: A CRC is defined by four parameters: polynomial, init, reflection and final XOR — the same "CRC16" name gives different results. MODBUS RTU sends the CRC low byte first — do not confuse display order with transmission order.