ISBN-13 check digit calculator



ISBN (International Standard Book Number) is a unique number assigned to each book.
ISBN-13:
    • The number has 12 information digits and ends with 1 check digit.
    • Assuming the digits are "abcdefghijkl-m" where m is the check digit. Then the check digit is computed by the following formula:
m = ( [a b c d e f g h i j k l] * [1 3 1 3 1 3 1 3 1 3 1 3] ) mod 10