Free tool

CAS Number Validator

Validate CAS Registry Numbers. Checks format, digit ranges, and the check digit algorithm.

What this tool checks

Checks

✓ Format: three groups separated by hyphens (XXXXXXX-XX-X)
✓ First part: 2-7 digits
✓ Second part: exactly 2 digits
✓ Third part: exactly 1 digit (the check digit)
✓ Check digit validation using the CAS algorithm

Does not check

✗ Whether the CAS number is actually registered
✗ Substance name, classification, or hazard information
✗ Whether the CAS number is deprecated or superseded
✗ EC number or EINECS cross-references

Tracking chemical substances across your catalog?

Rastro's AI agents validate CAS numbers, cross-reference SDS documents, and flag compliance gaps across your product data. Free demo on your use case.

Get a free demo

Related guides

Glossary

What is a CAS Number? Registry Numbers for Chemical Substances

A complete guide to CAS Registry Numbers: format, check digit algorithm, where they appear in product data, safety data sheets, and REACH compliance documentation.

Comparison

CAS Number vs EC Number: Which Chemical Identifier to Use

Compare CAS Registry Numbers and EC (EINECS/ELINCS) numbers: their formats, issuing authorities, regulatory contexts, and when to use each in product data and compliance documentation.