How this calculation works
Generate the final Luhn digit for an unsigned identifier body.
Double alternate digits from the right of the body, subtract nine from products above nine, then complete the next multiple of tenA worked example
For 7992739871, the weighted sum is 67 and the check digit is 3.
Good to know
Use a non-sensitive identifier. The value is limited to 12 digits.
Reference: NIST DLMF, Functions of Number Theory (opens in a new tab) ↗
Read the result
Generate the final Luhn digit for an unsigned identifier body.
The primary result is labeled “Check digit”. Keep the input definitions in view when comparing this result with another method.
Try a related calculation
Use a non-sensitive identifier. The value is limited to 12 digits.
For a related exercise, try the greatest common divisor.
A few questions, answered
How can I check the default inputs by hand?
For 7992739871, the weighted sum is 67 and the check digit is 3.
Which rule does this calculator apply?
Double alternate digits from the right of the body, subtract nine from products above nine, then complete the next multiple of ten