Enter ISBN-10 (first 9 characters):   Check Digit:

Enter ISBN-13 (first 12 characters):   Check Digit:

Enter ISBN-10 (all 10 characters):   ISBN-13:

Enter ISBN-13 (all 13 characters):   ISBN-10:

ISBN (International Standard Book Number) is a unique number assigned to each book.
ISBN-10:
    • The number has 9 information digits and ends with 1 check digit.
    • Assuming the digits are "abcdefghi-j" where j is the check digit. Then the check digit is computed by the following formula:
j = ( [a b c d e f g h i] * [1 2 3 4 5 6 7 8 9] ) mod 11
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