Modbus CRC-16 Calculator
Calculate the standard Modbus CRC-16 checksum for text or hexadecimal bytes.
What this tool calculates
Calculate the standard Modbus CRC-16 checksum for text or hexadecimal bytes. The main inputs on this page are Input, Input format. The result is intended to be readable immediately, with the explanation below available when you need to verify the method.
Method and calculation basis
Modbus RTU CRC-16 starts from 0xFFFF and uses polynomial 0xA001 with least-significant-bit-first processing. The transmitted CRC is low byte first.
Worked examples
Known small input
Use a short value whose output you can independently recognise before processing production data.
Byte-sensitive operations
For hashes and encodings, character encoding matters because the algorithm works on bytes, not visual text.
Understanding the result
The output should be read in the units shown beside the result. If you are comparing alternatives, keep all unchanged assumptions identical and alter one input at a time. That makes it easier to see which value is responsible for the difference.
Assumptions, edge cases and accuracy
A syntactically valid transformation is not necessarily safe or semantically correct for a production system. Check the relevant protocol, API, language or device specification.
Sources and methodology
- IETF / relevant standards body — Format and protocol definitions where applicable
- Language or device specification — Implementation-specific syntax and behaviour
Method reviewed for Instant Solvers V10.0 · October 2026. If you find a calculation or explanation that needs correcting, use the site Contact page and include the tool URL and the values you entered.