ISBN Validator: Check ISBN-10 and ISBN-13 Numbers

How to use this tool

Enter or choose an ISBN. Paste an ISBN-10 or ISBN-13, with or without an ISBN label, spaces, punctuation, or hyphens. The sample buttons demonstrate both formats and an incorrect check digit.
Review the check. The result shows whether the length, Bookland prefix, and check digit are valid. An incorrect check digit includes the expected final character.
Copy a converted value. When validation succeeds, use the row buttons to copy the ISBN-10 or ISBN-13 digits. A 979 ISBN has no ISBN-10 conversion.

ISBN-10 vs. ISBN-13 comparison

Feature	ISBN-10	ISBN-13
Length	10 characters	13 digits
Check digit	0–9 or X (=10)	0–9
Check calculation	Weights 10 down to 1; total is divisible by 11	First 12 digits alternate ×1 and ×3; total is divisible by 10
Prefix	None	978 or 979 (Bookland)
Used since	1970	2007 (global standard)
Conversion	Add 978 to the first nine digits and recalculate the check digit	Only 978 ISBN-13 numbers convert back to ISBN-10

How ISBN check digits work

An ISBN check digit helps catch common typing and transcription mistakes. For ISBN-10, multiply the first nine digits by weights 10 through 2, add those products, then choose a final value so the total is divisible by 11. The final value is 0–9 or X, where X represents 10. For example, a check digit of X is valid only in the tenth position.

ISBN-10: sum = d₁×10 + d₂×9 + … + d₉×2 + check; sum mod 11 = 0

For ISBN-13, multiply the first twelve digits by alternating weights of 1 and 3. The check digit is the value from 0 to 9 that makes the full weighted sum divisible by 10. A passing checksum catches many one-digit errors, but it does not establish that the number was assigned by an ISBN agency.

ISBN-13: check = (10 − (weighted sum mod 10)) mod 10

GS1 Bookland prefixes

ISBN-13 numbers use the 978 or 979 Bookland prefix. The 979 range expands the ISBN namespace; a 979 ISBN has no ISBN-10 equivalent because ISBN-10 conversion uses the 978 prefix. The 979-10 range is allocated to France's AFNIL agency. The 979-8 prefix is a United States registration group and includes some ISBNs issued through Amazon's publishing programs.

Validate and convert an ISBN

Paste an ISBN-10 or ISBN-13 to check its length, prefix, and check digit. The validator accepts common ISBN labels and punctuation along with spaces and hyphens, then shows unhyphenated digits that are easy to paste into a catalog or barcode workflow. If the check digit is wrong, the result displays the digit calculated from the preceding ISBN digits.

For example, a publisher preparing a product record can paste an ISBN from a manuscript or spreadsheet, verify the check digit, and copy the converted format for a form that requires ISBN-13. ISBN-10 and ISBN-13 are related formats, and ISBN-10 converts to a 978-prefixed ISBN-13. ISBN-13 values starting with 979 do not have an ISBN-10 equivalent.

ISBN hyphens depend on registration-group and publisher ranges, not on a fixed number of digits per group. This tool omits hyphens in its results rather than presenting approximate grouping as an official ISBN display. Add agency-range hyphenation only when the correct range data is available.

Frequently asked questions

Does a valid result confirm that a book exists?

No. A valid result means the number has an ISBN-10 or Bookland ISBN-13 structure and a matching check digit. This tool does not search publisher or library catalogs, so it cannot confirm that an ISBN is assigned to a published title.

Why does a 979 ISBN have no ISBN-10 equivalent?

ISBN-10 converts to ISBN-13 by adding the 978 prefix. ISBN-13 numbers beginning with 979 are outside that conversion range, so they do not have an ISBN-10 equivalent.

What does X mean in an ISBN-10?

X represents the value 10 when it is the final ISBN-10 check digit. It is not allowed elsewhere in an ISBN, and ISBN-13 uses a numeric check digit.

Do hyphens change the ISBN?

No. Spaces and hyphens only group digits for reading. Correct hyphen positions depend on ISBN registration-group range data, so this tool shows canonical unhyphenated digits instead of guessing those ranges.

How is the expected check digit calculated?

For ISBN-10, the first nine digits are weighted from 10 down to 2; the final digit makes the total divisible by 11, with X representing 10. For ISBN-13, the first twelve digits alternate weights of 1 and 3; the final digit makes the total divisible by 10.