ISBN Checker
Validate any ISBN and convert between ISBN-10 and ISBN-13 in seconds.
Valid ISBN — the check digit is correct.
ⓘValidates the check digit and converts between ISBN-10 and ISBN-13. A 13-digit ISBN starting 978 or 979 is also your book’s EAN — turn it into a scannable barcode with the ISBN Barcode Generator. UK ISBNs come from Nielsen.
Before you print, it is worth confirming your number is genuinely valid. This free ISBN checker validates any ISBN, tells you whether the check digit is correct, and flags typos that could stop your book scanning or selling. As an instant isbn validator, it removes the guesswork from one of the easiest mistakes to make when you are juggling several formats and a long list of numbers.
The tool also works as an ISBN 10 to 13 converter, switching cleanly between the two standards either way. That matters because older records use the 10-digit format while modern retail uses the 13-digit one. Use it to check isbn numbers across your paperback, hardback and ebook, confirm the isbn check digit, and make sure every number is right before it reaches your cover or your printer.
- Validate every ISBN as soon as you receive it from Nielsen.
- Keep the ISBN-13 version handy; it is what your barcode encodes.
- Give each format its own ISBN and check them all before printing.
- 01
Paste your ISBN
Enter your ISBN-10 or ISBN-13, with or without hyphens. The checker reads either format and ignores spacing so you can paste it straight in.
- 02
See if it is valid
The tool recalculates the check digit and tells you instantly whether the ISBN is valid or contains an error to correct.
- 03
Convert the format
Switch between ISBN-10 and ISBN-13 in one click, so you have the right version for retail, records or your barcode.
Common questions
- How do I check if an ISBN is valid?
- Every ISBN ends in a check digit calculated from the preceding numbers. If that digit does not match, the ISBN is invalid, usually from a typo. This checker recalculates it for you and confirms whether your ISBN is correct, so you can catch a mistake before it reaches your cover, barcode or distributor.
- What is an ISBN check digit?
- The check digit is the final character of an ISBN, derived mathematically from the other digits. It lets systems verify the number was entered correctly, much like a checksum. ISBN-10 and ISBN-13 use different formulas, which is why a single mistyped digit makes the whole number invalid. This tool validates the check digit for both formats.
- How do I convert ISBN-10 to ISBN-13?
- An ISBN-10 converts to ISBN-13 by prefixing 978, dropping the old check digit and recalculating a new one. The reverse is possible for 978 numbers but not for 979 ISBNs, which have no 10-digit equivalent. This converter handles the maths both ways automatically, giving you the correct format for retail or your records.
- Is an ISBN-13 the same as a barcode?
- Almost. An ISBN-13 beginning 978 or 979 is also your book's EAN, the number a retail barcode encodes. The barcode is simply that ISBN-13 rendered as scannable bars. Once you have confirmed your ISBN-13 is valid here, create the matching barcode for free with our ISBN Barcode Generator for your back cover.
- Where do UK authors get an ISBN?
- In the UK, ISBNs are issued by Nielsen, the official agency. You can buy a single number or a more economical block, and each format, paperback, hardback and ebook, needs its own ISBN. This checker does not issue numbers; use it to validate and convert the ISBNs you already hold before you print.
Ready to print your book properly?
Run the numbers with our free tools, then print with real UK book printers.