ISBN Check Digit Algorithms
ISBN-10: Sum of (digit x position) mod 11 = 0. Check digit can be 0-9 or X (10).
ISBN-13: Alternating weights of 1 and 3, sum mod 10 = 0.
ISBN-10 to ISBN-13: Prepend 978, drop old check digit, recalculate.
ISBN Calculator
Validate ISBN-10 and ISBN-13 check digits, convert between formats, and calculate missing check digits for book identification numbers.
Result
Enter an ISBN
ISBN-10
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ISBN-13
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Check Digit
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Format
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Validation Steps
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