How do I convert an ISBN-10 to an ISBN-13?

Put the 978 prefix in front of the first nine digits of the ISBN-10, throw away the old check character, then compute a fresh EAN-13 check digit. Example: ISBN-10 0-306-40615-2 keeps 030640615, becomes 978030640615, and the recomputed mod-10 check digit is 7, giving ISBN-13 978-0-306-40615-7. Only the first nine digits carry over; the tenth was a check character and is discarded.

How do I convert an ISBN-13 back to an ISBN-10?

Drop the 978 prefix, keep the next nine digits, then compute a fresh mod-11 check character. Example: 978-0-306-40615-7 loses the 978, keeps 030640615, and the recomputed check character is 2, giving ISBN-10 0-306-40615-2. The check character can be the letter X when its value is ten, as in 0-8044-2957-X.

Why does the check digit change when I convert?

ISBN-10 and ISBN-13 use different math. ISBN-10 weights the nine body digits by 10 down to 2 and takes the remainder modulo 11, so the check value can be 0 to 10, with 10 written as X. ISBN-13 is an EAN-13 barcode: digits are weighted 1 and 3 alternately and the total is taken modulo 10, so the check digit is always 0 to 9. Same book, two unrelated formulas, so the trailing character almost always differs.

Why can a 979 ISBN-13 not become an ISBN-10?

ISBN-10 only ever lived inside the 978 Bookland range. When that range filled up, the 979 prefix was opened to add more numbers, and those titles were never assigned an ISBN-10. So a code like 979-12-200-0000-X has no ten-digit form. This tool detects a 979 prefix and tells you there is no ISBN-10 rather than producing a wrong number.

What is the X at the end of some ISBN-10 numbers?

The ISBN-10 check character is a value from 0 to 10. When it lands on 10 there is no single digit for it, so the standard uses the Roman numeral X. It only ever appears in the last position, as in 0-8044-2957-X. ISBN-13 never uses X because its modulo-10 check digit is always a single digit 0 to 9.

Does it matter if my ISBN has hyphens or spaces?

No. The tool strips every hyphen and space before it does anything, so 978-0-306-40615-7, 978 0 306 40615 7 and 9780306406157 are all read as the same code. It shows the result both as plain digits and in a readable hyphenated grouping so you can copy whichever form your catalog or store listing expects.

Match a print ISBN-13 to an old ISBN-10 record

Your library catalog stored a book under its ISBN-10 years ago, but the new shipment is labeled only with an ISBN-13. Paste the 978-prefixed ISBN-13, get the exact ISBN-10 back, and the two records line up so the copy merges instead of creating a phantom duplicate. The check character is recomputed, so an X at the end is filled in correctly rather than guessed.

Build an Amazon ASIN-style lookup from a 13-digit code

Some marketplaces and affiliate links still key on the ISBN-10 form (it doubles as the legacy ASIN for books). When your supplier feed only carries ISBN-13, convert each 978 code down to its ISBN-10 so your product URLs and lookups resolve. 979 titles are flagged as having no ISBN-10 so you do not silently ship a broken link.

Normalize a messy bibliography to one ISBN format

A reference list pasted from three sources mixes ten-digit and thirteen-digit ISBNs with random hyphenation. Run each through the converter to land them all on ISBN-13, the current standard, with a consistent hyphenated grouping. The plain-digits output drops cleanly into a CSV column for your citation manager.

Verify a barcode before sending artwork to print

A cover designer receives an ISBN-10 from the author but the barcode on the back cover must encode the EAN-13. Convert the ISBN-10 to its 978 ISBN-13, confirm the recomputed check digit, then hand the thirteen-digit number to the barcode generator. No transposed digit slips through to a printed run of a thousand jackets.

ISBN-10 to ISBN-13 Converter (and back)

Convert ISBN-10 ⇄ ISBN-13 with the check digit recomputed — 978 prefix, mod-10 and mod-11, hyphen-aware, browser-only

Runs locally
Category Developer & DevOps
Best for Formatting, validating, shrinking, or inspecting code-adjacent text.

ISBN to convert

Paste an ISBN-10 or ISBN-13. Hyphens and spaces are ignored.

Enter an ISBN above to convert it to the other length.

What this tool does

Free ISBN converter that turns an ISBN-10 into an ISBN-13 and back, with the check digit recomputed from scratch every time. To go from ISBN-10 to ISBN-13 the tool prepends the 978 Bookland prefix to the first nine digits, drops the old mod-11 check character and computes the EAN-13 mod-10 check digit. To go the other way it strips the 978 prefix, keeps the next nine digits and recomputes the mod-11 check character, which can be the letter X for the value ten. A 979-prefixed ISBN-13 has no ISBN-10 equivalent, and the tool says so rather than inventing one. Hyphens and spaces are ignored, so you can paste straight from a copyright page or a catalog record. Output appears both as a plain run of digits and in a readable hyphenated form, each with one-click copy. Everything runs in your browser. Nothing is uploaded.

Tool details

Input: Files; The page exposes text boxes, numeric controls, file pickers, or structured inputs depending on the tool.
Output: Live result + Copy; The result area focuses on usable output, with copy, download, or preview actions when supported.
Privacy: Browser-side processing; The main tool logic does not call an external API, so inputs normally stay in the current tab.
Save / share: Shareable URL state; Key settings are encoded in the URL so another person can reopen the same setup.
Performance budget: Initial JS <= 9 KB; No WASM budget is declared, keeping the tool quick to open on mobile.
Best fit: Developer & DevOps · Developer; Category and role tags drive related tools, internal links, and quick fit checks.

How to use

1. Input

Paste or drop your content into the tool panel.
2. Process

Click the button. All processing is local in your browser.
3. Copy / Download

Copy the result or download to disk in one click.

How ISBN-10 to ISBN-13 Converter fits into your work

Use it in the small gaps between coding, reviewing, debugging, and shipping.

Developer jobs

Formatting, validating, shrinking, or inspecting code-adjacent text.
Preparing snippets for documentation, tickets, commits, or handoff.
Checking a small payload quickly without switching tools.

Developer checks

Run irreversible transforms like minify or obfuscate on a copy.
Keep secrets out of pasted snippets unless the tool explicitly stays local.
Use your normal tests or linter before shipping transformed code.

Good next steps

These links move the current task into a more complete workflow.

Real-world use cases

Match a print ISBN-13 to an old ISBN-10 record
Your library catalog stored a book under its ISBN-10 years ago, but the new shipment is labeled only with an ISBN-13. Paste the 978-prefixed ISBN-13, get the exact ISBN-10 back, and the two records line up so the copy merges instead of creating a phantom duplicate. The check character is recomputed, so an X at the end is filled in correctly rather than guessed.
Build an Amazon ASIN-style lookup from a 13-digit code
Some marketplaces and affiliate links still key on the ISBN-10 form (it doubles as the legacy ASIN for books). When your supplier feed only carries ISBN-13, convert each 978 code down to its ISBN-10 so your product URLs and lookups resolve. 979 titles are flagged as having no ISBN-10 so you do not silently ship a broken link.
Normalize a messy bibliography to one ISBN format
A reference list pasted from three sources mixes ten-digit and thirteen-digit ISBNs with random hyphenation. Run each through the converter to land them all on ISBN-13, the current standard, with a consistent hyphenated grouping. The plain-digits output drops cleanly into a CSV column for your citation manager.
Verify a barcode before sending artwork to print
A cover designer receives an ISBN-10 from the author but the barcode on the back cover must encode the EAN-13. Convert the ISBN-10 to its 978 ISBN-13, confirm the recomputed check digit, then hand the thirteen-digit number to the barcode generator. No transposed digit slips through to a printed run of a thousand jackets.

Common pitfalls

Keeping the old check digit when prepending 978. The ISBN-10 check character is computed differently from the ISBN-13 one, so 978 plus the full ten-digit ISBN-10 is almost always wrong. Only the first nine digits carry over, and a brand-new mod-10 digit is computed at the end.
Trying to turn a 979 ISBN-13 into an ISBN-10. The 979 range was opened after ISBN-10 ran out, so those titles have no ten-digit form at all. If a tool hands you an ISBN-10 for a 979 code, it fabricated it. This converter refuses and tells you why.
Dropping the X or treating it as a digit. The trailing X in an ISBN-10 stands for the value ten and is part of the number. Deleting it or reading it as a zero breaks validation and the round trip back to ISBN-13. Copy the whole value, X included.

Privacy

Every step — stripping hyphens, detecting the length, recomputing the mod-10 or mod-11 check digit, and the conversion itself — is plain JavaScript running in your browser tab. No ISBN is uploaded and nothing is logged. The one caveat: the shareable link puts the ISBN in the query string, so a link pasted into chat records that ISBN in the recipient server access log. If a code is confidential before publication, use the copy button and paste the result instead of sharing the URL.

FAQ

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ISBN-10 to ISBN-13 Converter (and back)

What this tool does

Tool details

How to use

1. Input

2. Process

3. Copy / Download

How ISBN-10 to ISBN-13 Converter fits into your work

Developer jobs

Developer checks

Good next steps

Real-world use cases

Match a print ISBN-13 to an old ISBN-10 record

Build an Amazon ASIN-style lookup from a 13-digit code

Normalize a messy bibliography to one ISBN format

Verify a barcode before sending artwork to print

Common pitfalls

Privacy

FAQ

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