How is an EAN-13 check digit calculated?

Take the 12 body digits and read them from right to left, multiplying alternately by 3 then 1. Sum every product, then the check digit is the smallest number that makes the total a multiple of ten. For 400638133393 the weighted sum is 109, the next multiple of ten is 110, so the check digit is 1 and the full barcode is 4006381333931. The tool shows this sum so you can follow the arithmetic.

What is the difference between EAN-13 and UPC-A?

UPC-A is the 12-digit code used mostly in North America, EAN-13 is the 13-digit international superset, and a UPC-A is really an EAN-13 with a leading zero. Both use the exact same mod-10 weighting, the only practical difference is length: enter 11 body digits and you get a UPC-A, enter 12 and you get an EAN-13. Convert a UPC to EAN-13 by prefixing 0, the check digit stays identical.

Why do odd and even positions get weighted by 3 and 1?

Alternating weights of 3 and 1 are what let the checksum catch errors. A weight of 1 on one set of positions and 3 on the other means a single mistyped digit always changes the weighted sum, and most swaps of two neighbouring digits change it too, because 3 and 1 are different. Counting from the rightmost body digit, that nearest digit is weighted 3, the next 1, and so on alternating to the left.

How do I verify that a full barcode is correct?

Paste the complete number, all 13, 12 or 8 digits, and the tool recomputes the check digit from the body and compares it with the last digit you typed. If they match the barcode passes, if not it fails and you know there is a typo. For example 4006381333931 passes but 4006381333930 fails, because the real check digit for that body is 1, not 0.

Does an EAN-8 use the same formula?

Yes. EAN-8 is the short 8-digit barcode used on small packs where a full EAN-13 will not fit, like a pack of chewing gum. It has 7 body digits plus a check digit and uses the identical mod-10 weighting of 3 and 1 from the right. For body 9638507 the check digit is 4, giving the full code 96385074. Enter 7 digits here and the tool treats it as EAN-8 automatically.

What does the check digit actually protect against?

A single check digit catches every single-digit error and most transposition errors, which are the two most common ways a human mistypes a barcode at a keyboard. It does not prove the barcode belongs to a real product or is registered with GS1, only that the number is internally consistent. A made-up string can still pass the checksum by chance, so passing means well-formed, not genuine.

Generate a print-ready EAN-13 from a 12-digit GTIN body

Your GS1-assigned company prefix and item number give you 12 digits, but the barcode font needs all 13. Paste the body, read off the check digit, and copy the completed code straight into your label artwork. One wrong digit here means a reprinted proof, so verifying it before the file leaves your hands saves the press run.

Audit a marketplace product feed for keying errors

Before a CSV of GTINs uploads to Amazon or a retailer portal, paste any suspect code in verify mode to see pass or fail instantly. Since the mod-10 check catches every single-digit slip and most adjacent swaps, a failing verdict almost always marks a real typo in that row, not a false alarm.

EAN / UPC Check Digit Calculator: EAN-13, UPC-A, EAN-8

Compute or verify the check digit for EAN-13, UPC-A and EAN-8 barcodes, mod-10 weighting with the odd and even positions, browser-only

Runs locally
Category Developer & DevOps
Best for Checking file type, size, metadata, and obvious mismatch signals before sharing.

Mode

Body without check digit

Enter digits above to see the result.

What this tool does

Free EAN / UPC check digit calculator that computes and verifies the last digit of EAN-13, UPC-A and EAN-8 retail barcodes. Every GS1 barcode ends in a check digit derived from the digits before it: read each digit from the right, multiply by 3 and 1 alternately, sum the products, and the check digit is whatever brings that sum up to the next multiple of ten. Paste a body without its last digit and the tool returns the digit you need, then prints the completed barcode ready to copy. Paste a full code and it tells you pass or fail, so a mistyped number gets caught before it reaches a label printer or a product feed. Length picks the symbology for you: twelve body digits means EAN-13, eleven means UPC-A, seven means EAN-8. Spaces and hyphens are ignored on input. Everything runs in your browser with one-click copy and a shareable link, no upload and no GS1 account.

Tool details

Input: Text; 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 EAN / UPC Check Digit Calculator fits into your work

Use it before upload, handoff, archive, support review, or any moment where a file needs one local check before it leaves your machine.

File jobs

Checking file type, size, metadata, and obvious mismatch signals before sharing.
Preparing mixed folders for upload, archive, intake, or review.
Keeping sensitive files in the browser instead of sending them to an account-based service.

File checks

Do not treat the extension alone as proof of the real file type.
Review metadata before a file goes to customers, vendors, or a public page.
Keep the original file until the copied, converted, or exported result is verified.

Good next steps

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

Real-world use cases

Generate a print-ready EAN-13 from a 12-digit GTIN body
Your GS1-assigned company prefix and item number give you 12 digits, but the barcode font needs all 13. Paste the body, read off the check digit, and copy the completed code straight into your label artwork. One wrong digit here means a reprinted proof, so verifying it before the file leaves your hands saves the press run.
Audit a marketplace product feed for keying errors
Before a CSV of GTINs uploads to Amazon or a retailer portal, paste any suspect code in verify mode to see pass or fail instantly. Since the mod-10 check catches every single-digit slip and most adjacent swaps, a failing verdict almost always marks a real typo in that row, not a false alarm.

Common pitfalls

Pasting a full 13-digit code into compute mode. Compute needs the 12-digit body only; feeding it the whole code calculates a check digit for the wrong number. Use verify mode for complete codes.
Forgetting that the weighting starts from the rightmost body digit, not the left. On odd-length bodies, counting from the left swaps which positions get 3 and which get 1, yielding a plausible but wrong digit.
Reading a UPC-A as needing a different formula. It is an EAN-13 with a leading zero and uses the identical mod-10 weighting, so the check digit is the same once you pad it.

Privacy

Every digit, the weighting, the running sum and the pass-or-fail verdict are computed by JavaScript inside your browser tab. No barcode, GTIN or product number is sent to any server or logged anywhere. Note that the shareable link writes your input into the URL, so for an unreleased product code copy the text instead of sharing the link.

FAQ

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EAN / UPC Check Digit Calculator: EAN-13, UPC-A, EAN-8

What this tool does

Tool details

How to use

1. Input

2. Process

3. Copy / Download

How EAN / UPC Check Digit Calculator fits into your work

File jobs

File checks

Good next steps

Real-world use cases

Generate a print-ready EAN-13 from a 12-digit GTIN body

Audit a marketplace product feed for keying errors

Common pitfalls

Privacy

FAQ

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