📊 Barcode Check Digit Validator (EAN, UPC, ISBN, ISSN)
Paste a barcode, ISBN or ISSN and instantly see whether its check digit is correct — or enter the digits without it to get the complete number.
EAN-13 / GTIN-13
✓ ValidCheck digit is 1; the correct check digit for this number is 1.
ISBN-13
✓ ValidCorrect check digit: 1.
Validates the check digit of EAN-13, UPC-A, EAN-8 and GTIN-14 barcodes, plus ISBN-10/13 and ISSN. The check digit is the last digit, computed from all the others by a fixed formula (GS1 mod-10, or mod-11 for ISBN-10/ISSN) — so a single mistyped or transposed digit almost always fails the check. Enter the digits without the check digit and the tool tells you the complete barcode. 🔒 All computed in your browser.
How the barcode check digit validator (ean, upc, isbn, issn) works
Every retail barcode and book/serial number ends in a check digit calculated from all the preceding digits by a fixed formula: EAN/UPC/GTIN use the GS1 mod-10 scheme (weights of 3 and 1), while ISBN-10 and ISSN use a mod-11 scheme (which is why their last character can be an X). This tool detects the format from the length, recomputes the check digit, and tells you whether the one in your number matches. Enter the digits without the final check digit and it returns the complete, valid barcode instead.
The check digit exists to catch data-entry mistakes: it detects every single-digit error and most adjacent transpositions (swapping two neighbouring digits), which are the most common typing slips. A failing check almost always means the number was mistyped or misread — though a passing check only proves the number is well-formed, not that the product, book or journal actually exists. This validates GTIN-8/12/13/14, ISBN-10/13 and ISSN; it doesn't decode what the barcode refers to. Everything runs in your browser.
Frequently asked questions
What is a barcode check digit?
The final digit of a barcode, calculated from all the others by a fixed formula. Scanners recompute it and compare — if it doesn't match, the scan is rejected as a misread. It's a built-in error-detection digit, not part of the product identity.
How is the EAN-13 / UPC check digit calculated?
Using the GS1 mod-10 method: from the right, multiply the data digits alternately by 3 and 1, sum them, and the check digit is whatever makes that total a multiple of 10. This tool shows the expected value so you can see if yours matches.
Why do some ISBNs and ISSNs end in X?
ISBN-10 and ISSN use a mod-11 check, so the check value can be 10 — written as the single character X. ISBN-13 (which is an EAN-13) uses mod-10, so its check digit is always 0–9.
Can I find a missing check digit?
Yes — enter the barcode's data digits without the final check digit (e.g. 12 digits for an EAN-13) and the tool appends the correct check digit to give you the complete number.
Does a valid check digit mean the product exists?
No. The check digit only confirms the number is internally consistent (not mistyped). It says nothing about whether the barcode is assigned to a real product — only the brand owner's GS1 registration does that.
Is my data uploaded?
No — validation runs entirely in your browser and works offline.