What Is a CAS Number?
Published 2025-01-14
A CAS Registry Number is the universal identifier for a chemical substance, independent of name or language.
A CAS Registry Number uniquely identifies a chemical substance regardless of the name used to describe it. The format is up to ten digits split into three parts separated by hyphens, for example 50-00-0. The final digit is a check digit calculated from the preceding digits, which makes it possible to validate a CAS Number before searching a database. Because chemical names differ between languages, suppliers and regulatory systems, the CAS Number is the most reliable key for sourcing, documentation and regulatory filings.