How does ISBN-10 become ISBN-13?

You drop the ISBN-10 check digit, prefix the EAN code 978 to the remaining 9 digits, then compute a fresh ISBN-13 check digit. The first nine significant digits are otherwise unchanged.

Why does the new check digit differ from the old one?

ISBN-10 uses a modulo-11 checksum with weights 10 down to 1, while ISBN-13 uses a modulo-10 checksum with alternating weights 1 and 3. Different schemes over different digits produce different check digits.

What does the X in an ISBN-10 mean?

The ISBN-10 check digit can be 0 through 10, and 10 is written as the letter X because it needs a single character. The tool accepts X and treats it as the value 10 when validating.

Can every ISBN-10 be converted?

Yes. Every valid ISBN-10 maps to exactly one ISBN-13 using the 978 prefix. The reverse is not true, because newer ISBN-13 numbers using the 979 prefix have no ISBN-10 equivalent.

Is the hyphenation accurate?

The hyphenated grouping shown is illustrative. Correct group, registrant, and publication boundaries depend on the registration agency and vary by length, so always use the publisher's official hyphenation for print.

What is the ISBN-10 to ISBN-13 Converter?

Convert a valid ISBN-10 book number into its ISBN-13 equivalent by prefixing 978 and recomputing the modulo-10 check digit. Validates the original ISBN-10 check digit first, handles the X check character, and offers hyphenated output. Runs in your browser. It runs free in your browser on Gera Tools, with nothing uploaded.

ISBN-10 to ISBN-13 Converter

Name: ISBN-10 to ISBN-13 Converter
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

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ISBN-13 replaced the older 10-digit ISBN in 2007, and every ISBN-10 has an exact 13-digit equivalent. This converter validates your ISBN-10, then performs the standard transformation: keep the meaningful digits, add the 978 prefix, and recompute the check digit under the newer scheme.

How it works

The conversion is mechanical once the original number is verified:

1. Validate ISBN-10:  sum of digit × (10,9,...,1) is divisible by 11 (X = 10)
2. Drop the ISBN-10 check digit, keep the first 9 digits
3. Prefix "978" to make a 12-digit body
4. ISBN-13 check = (10 − (sum of digit×[1,3,1,3,...]) mod 10) mod 10

The first nine information digits carry the registration group, publisher, and title and are preserved unchanged; only the prefix and check digit are new. Because the two formats use different checksum algorithms, the check digit almost always changes during conversion.

A concrete conversion walkthrough

Take the ISBN-10 0-306-40615-2. The validation step computes 0×10 + 3×9 + 0×8 + 6×7 + 4×6 + 0×5 + 6×4 + 1×3 + 5×2 + 2×1 = 143, which is divisible by 11, so the number is valid.

Conversion then:

Drops the trailing 2 and keeps 030640615.
Prepends 978 to make the 12-digit body 978030640615.
Computes the EAN-13 check digit: weight the 12 digits with alternating 1 and 3, sum them, take the result mod 10, subtract from 10, and that mod 10 gives 7.
Final ISBN-13: 978-0-306-40615-7.

Notice the check digit changed from 2 to 7 — this is normal and always expected because the two algorithms are completely different.

When would you need this conversion?

Library cataloguing: older library records used ISBN-10; modern systems expect ISBN-13 (EAN-13 barcodes).
E-commerce product listings: platforms such as Amazon and bookshops now index by ISBN-13, so if you only have the ISBN-10 from a printed book you need to convert.
Database migration: a book database built before 2007 likely stores ISBN-10 values; converting them to ISBN-13 aligns with current standards.
Barcode generation: ISBN-13 is a valid EAN-13 barcode — scanning the cover barcode of any book since 2007 will give the ISBN-13.

The 979 prefix and why it cannot be reversed

All conversions from ISBN-10 use the 978 prefix — that is the only EAN prefix originally allocated for books. Since 978 numbers began running low, the 979 prefix was introduced for new ISBN-13 numbers, but these have no ISBN-10 equivalent. This means conversion only runs in one direction: ISBN-10 always maps to a 978-prefix ISBN-13, but not all ISBN-13 numbers can be reduced to an ISBN-10.

Notes

The tool will not convert a number whose ISBN-10 check digit is wrong, which catches typos before they propagate. Hyphens and spaces are stripped automatically, so you can paste the number as printed. Hyphenation in the output is illustrative only — exact group and publisher boundaries depend on the registration agency.