Checksum Calculator

Online checksum calculator for CRC32, CRC16/IBM, Adler-32, SUM, XOR, and cryptographic digests (MD5, SHA-1, SHA-256). Paste text or hex data and verify integrity instantly.

Input data

Affects the displayed checksum for CRC values (useful for Modbus or device docs).

Hex bytes can be space-separated or continuous. Text input uses raw ASCII codes.

How to Use This Calculator

Paste your payload, choose an algorithm, and hit Calculate. Text input reads ASCII codes directly. Hex accepts spaces, commas, or continuous digits.

  1. Set Input type to Text/ASCII or Hex bytes depending on your data source.
  2. Pick the desired checksum algorithm. CRCs and Adler are fast hardware-friendly models; MD5/SHA require WebCrypto support.
  3. Toggle CRC byte order to match your device (little-endian for Modbus style, big-endian for network specs).
  4. Click Calculate. The result box updates with the hex checksum; decimal is shown when applicable.

Methodology

A checksum is a compact integrity check created by running your data through a deterministic algorithm. The receiver recomputes the same checksum and compares values to detect accidental corruption.

This calculator mirrors how embedded and networking devices derive CRCs and simple sums. CRC-32 uses poly 0xEDB88320 with standard init/final XOR, CRC-16/IBM uses poly 0xA001, and Adler-32 runs modulo 65521 accumulators. Simple SUM/N XOR operations keep within the expected modulus.

  • CRC / sums (CRC16, CRC32, SUM-8) match common serial protocols, CAN, Modbus, and field instrumentation.
  • MD5 / SHA are cryptographic hashes exposed via WebCrypto; MD5 is historically used for integrity checks while SHA-256 is preferred today.
  • Results display the checksum in hex plus a decimal value when the output fits a standard integer. Digest algorithms only show the hex string.
Figures are estimates and reflect the algorithms described above. Verify with vendor documentation for production-critical workflows.

Full original guide (expanded)

The previous layout included a skip link titled "Skip to main content" and a longer descriptive header about checksum workflows; this section preserves that guidance.

Related Technical Pages

Tips

If your device reports CRC bytes swapped, toggle the "CRC byte order" select to match (little-endian vs big-endian).

Formulas

CRC-32: polynomial 0xEDB88320, init 0xFFFFFFFF, reflected input/output, final XOR 0xFFFFFFFF generates a 32-bit result.

CRC-16 / IBM: poly 0xA001 with init 0xFFFF and low-byte first processing.

Adler-32: two accumulators A and B mod 65521 produce a 32-bit pair (B << 16 | A).

SUM, XOR: modular reductions (mod 256 or 65535) and byte-wise XOR match embedded implementations.

MD5 / SHA-1 / SHA-256: computed through WebCrypto to deliver digest hex strings, no decimal representation.

Citations

NIST — Weights and measures — nist.gov · Accessed 2026-01-19
https://www.nist.gov/pml/weights-and-measures

FTC — Consumer advice — consumer.ftc.gov · Accessed 2026-01-19
https://consumer.ftc.gov/

Changelog
Version: 0.1.0-draft · Last code update: 2026-01-19
  • Initial audit spec draft generated from HTML extraction (review required).
  • Verify formulas match the calculator engine and convert any text-only formulas to LaTeX.
  • Confirm sources are authoritative and relevant to the calculator methodology.
✓ Verified by Ugo Candido Last Updated: 2026-01-19 Version 0.1.0-draft
Version 1.5.0