Internet Checksum Calculator
Enter hexadecimal data to compute its RFC 1071 Internet checksum.
Result
How to use
- Enter your values in the fields above.
- Press Calculate to see your result instantly.
- Use the Share button to copy a link to your result.
About this calculator
This calculator computes the Internet checksum defined in RFC 1071: split the data into 16-bit words, sum them using one's-complement arithmetic (any carry out of the top bit wraps back into the sum), then take the one's complement of the final result. It's a lightweight error-detection code, not a cryptographic hash.
This exact algorithm is what protects the header of every IPv4, TCP and UDP packet on the internet — the receiving side recomputes the checksum and drops the packet if it doesn't match, catching transmission errors introduced anywhere along the path.
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