title: What algorithm to use to calculate a check digit?
body: <p>What algorithm to use to calculate a check digit for a list of digits?<br>
  The length of the list is between 8 and 12 digits.</p>
  
  <p>see also:<br>
  <a href="https://stackoverflow.com/questions/46231/how-to-generate-a-verification-code-number">How to generate a verification code/number?</a></p>