Reference Data · Validation

Check Digit Calculator

Compute and validate check digits (Luhn, mod-10/11/97, Damm, Verhoeff).

Check Digit Calculator

Compute or validate check digits locally — Luhn, mod-10/11/97, Damm and Verhoeff.

Computed

Input

AlgorithmISO/IEC 7812-1 — used for PANs and many account numbers.NumberWhitespace and hyphens are ignored. Mod-11 may end with 'X'.

Runs entirely in your browser. No value leaves the page or is persisted.

Output

Check digit

Steps (1)

Probe digits 0–9 with luhnCheck; digit 3 makes 79927398713 sum to a multiple of 10.

Diagnostic JSON

{
  "input": "7992739871",
  "algorithm": "luhn",
  "checkDigit": "3",
  "fullNumber": "79927398713",
  "isValid": false,
  "explanation": [
    "Probe digits 0–9 with luhnCheck; digit 3 makes 79927398713 sum to a multiple of 10."
  ],
  "errors": []
}