Luhn Check Digit Calculator
Find the last digit that makes a number pass the Luhn (mod 10) algorithm.
Tool inputs stay in your browser · optional AI search sends your query
Good to know: Works for card numbers, IMEIs and any Luhn-protected ID. Enter the number WITHOUT its last digit.
How to use it (step by step)
- 1Fill in the boxes: “Number without check digit”. Example numbers are already there so you can see how it works; replace them with yours.
- 2The result updates instantly as you type (on a phone it is below the boxes).
- 3The bold line is the main answer. Tap Copy next to any value to copy it.
Words to know
- Luhn check
- A quick math test every real card number passes, like a spelling check for numbers. Passing it only means the number is typed in the right shape, not that the card is real.
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