ISO 7064 Check Character Calculator

About this calculator

The ISO 7064 check character calculator appends a verification character to an identifier using one of the standard's algorithms: MOD 11,10 for purely numeric strings, or MOD 37,36 for alphanumeric strings (letters A–Z plus digits 0–9). Both work by processing the value digit by digit, applying a running modular calculation with a fixed radix, and deriving a single check character designed to catch the most common data-entry mistakes — a single mistyped character or two adjacent characters swapped (transposition).

ISO/IEC 7064 is the international standard behind check-digit schemes used in identifiers such as the International Standard Audiovisual Number (ISAN) and various national registration and organization codes, where a simple typo could otherwise route a document or payment to the wrong record. Software developers implementing ID validation, and standards or compliance teams use this calculator to verify that a generated identifier's check character is correct, or to compute the missing check character for a new one.