How to use
- Enter a barcode number. With 7, 11, 12 or 13 digits (no check digit) the tool calculates the check digit; with a complete 8, 12, 13 or 14-digit number it validates it.
- Twelve and thirteen digits can be read two ways, so choose how to treat them at the top: 12 digits is either “calculate an EAN-13 check digit” or “validate a UPC-A”; 13 digits is either “calculate a GTIN-14 check digit” or “validate an EAN-13”.
- Have a list? Switch to Batch and paste one number per line. Copy table (TSV) pastes straight into Excel or Google Sheets.
GTIN formats
| Format | Digits | Barcode | Typical use |
|---|---|---|---|
| GTIN-8 | 8 | EAN-8 | Packs too small for a full barcode |
| GTIN-12 | 12 | UPC-A | US and Canadian retail |
| GTIN-13 | 13 | EAN-13 | Retail in most other countries |
| GTIN-14 | 14 | ITF-14, GS1-128 | Cases and cartons |
How the check digit works (GS1 mod-10)
- Starting from the rightmost digit (excluding the check digit), multiply digits alternately by 3 and 1.
- Add up the products.
- Subtract the remainder of the sum divided by 10 from 10. If the result is 10, the check digit is 0.
Worked example for the UPC-A 03600029145:
| Digit | 0 | 3 | 6 | 0 | 0 | 0 | 2 | 9 | 1 | 4 | 5 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Weight | 3 | 1 | 3 | 1 | 3 | 1 | 3 | 1 | 3 | 1 | 3 |
| Product | 0 | 3 | 18 | 0 | 0 | 0 | 6 | 9 | 3 | 4 | 15 |
The products add up to 58; 58 mod 10 is 8, and 10 − 8 = 2, so the full number is 036000291452. Because the weights are counted from the right, the same procedure works for EAN-8, UPC-A, EAN-13 and GTIN-14.
Prefixes and issuing organizations
The first three digits (in GTIN-13 form) are the GS1 prefix, which identifies the GS1 member organization that issued the number. UPC-A numbers become 0 + 12 digits, so a code starting with 0 or 1 falls in GS1 US ranges; 500–509 is GS1 UK, 400–440 GS1 Germany, 880 GS1 Korea. 978–979 are books (ISBN), 977 serials (ISSN), and 200–299 are restricted-circulation numbers used only inside a store or company.
A prefix is not a country of origin. A US brand that manufactures overseas still uses its GS1 US prefix, and a product with a 690 prefix may be made outside China. This tool uses a short list of well-known ranges; GS1’s official “GS1 Prefixes” list is the complete reference.
Things to watch
- Toolulah does not issue GTINs. Numbers for products you sell must be built from a company prefix licensed by GS1 — GS1 US, GS1 UK or the member organization in your country. A made-up number with a valid check digit can still clash with another company’s product.
- A correct check digit only means no typo was detected, not that the number is registered. The scheme catches every single-digit error and every swap of two adjacent digits except when they differ by 5 (for example 1↔6).
- Once a number checks out, draw it with the barcode generator.
FAQ
Is a UPC-A the same as an EAN-13?
Adding a leading 0 to a UPC-A gives the same GTIN in EAN-13 form, and the check digit does not change because the leading zero adds nothing to the sum: 036000291452 ↔ 0036000291452.
Does a 690 prefix mean the product is made in China?
No. It only means GS1 China issued the number. The same applies to every prefix.
Can I make my own numbers for in-store use?
Numbers starting with 2 are reserved for restricted circulation — in-store or internal use — but they must never be used on products sold through other retailers or online.