Barcode Check Digit Calculator

Calculate or validate UPC, EAN, GTIN and SSCC check digits with the GS1 modulo-10 method. Auto-detect likely identifier roles, expose ambiguous lengths, and inspect every ×3/×1 weighting step before you use the completed number.

Calculate or validateAuto-detect + ambiguity×3 / ×1 weighting traceGTIN · UPC · EAN · SSCC

GS1 check digit studio

Calculate or validate GS1 Mod-10 check digits

Work with GTIN-8, UPC / GTIN-12, EAN / GTIN-13, GLN, GTIN-14 and SSCC-18. Preserve leading zeros, see every ×3 / ×1 step, audit batches, and export the result without sending identifier data to a server.

Calculate · validate · trace · batch

Enter the identifier without its final check digit.

Identifier digitsGS1 key / format

Result036000291452

GTIN-12 / UPC-A · check digit 2

Weighted sum 58 · remainder 8 · check digit 2

Body03600029145

Weighted sum58

Remainder8

Check digit2

Quick example

Exact Mod-10 arithmetic

Starting at the rightmost body digit, multiply by 3, then 1, alternating leftward. The check digit is the amount needed to reach the next multiple of 10.

check = (10 − (weighted sum mod 10)) mod 10

Position	Digit	Weight	Product
Enter digits to see the arithmetic.

GTIN-13 and GLN are both 13 digits and use the same GS1 Mod-10 arithmetic. Choose the explicit format when the business meaning matters.

Important: a matching check digit validates arithmetic structure only. It does not allocate a GS1 identifier, prove ownership, confirm registration, or certify scanner / retailer acceptance.

Batch calculate or validate — up to 1,000 rows

Paste one identifier per line. Invalid rows remain visible with a reason instead of disappearing from the audit.

IdentifiersBatch modeFormat

Ready.

#	Input	Format	Complete identifier	Status

Recent checks

Optional recent history stays in this browser. Portable links include the current single identifier state in the URL hash.

Ready. Spaces and hyphens are ignored; other non-digits are rejected.

GS1 check digits: what this calculator proves

The final digit in common GS1 keys is a Modulo-10 check digit designed to catch many data-entry errors. This Studio calculates or validates that arithmetic for the identifier lengths below, while keeping the business meaning and allocation boundary explicit.

GTIN-87-digit body + check digit. Used for compact retail item numbering.

GTIN-12 / UPC-A11-digit body + check digit. Common North American retail form.

GTIN-13 / EAN-1312-digit body + check digit. Leading zeros are significant and preserved.

GLN13-digit GS1 location number. Same Mod-10 arithmetic as GTIN-13, different business purpose.

GTIN-1413-digit body + check digit for 14-digit trade-item identification.

SSCC-1817-digit body + check digit for Serial Shipping Container Codes.

Why the weights alternate 3 and 1

GS1 Mod-10 starts from the right side of the body. Multiply the rightmost body digit by 3, the next by 1, and keep alternating leftward. Add the products. The final check digit makes the total a multiple of 10. The trace above exposes each product so you can audit a result instead of trusting a black box.

Calculation is not allocation

A correct check digit does not prove that a company is licensed to use the number, that the number belongs to a specific product or location, or that a printed symbol meets barcode-quality requirements. For allocation, ownership and official identifier services, use the relevant GS1 organization and records.

Reference: GS1 Check Digit Calculator and GS1 US Check Digit Calculator. WebToolArc performs the arithmetic locally in your browser.

When to calculate and when to validate

Choose Calculate missing digit when you have the body of a GS1 key and need its final check digit. Choose Validate complete ID when the identifier already includes a final digit and you want to compare it with the Mod-10 result. For bulk cleanup, use the batch workflow so invalid rows remain visible instead of being silently discarded.

Leading zeros and pasted formatting

Identifiers are treated as digit strings rather than ordinary numbers, so leading zeros are preserved. Spaces and hyphens are removed for convenience; letters and other characters are rejected because silently coercing them can change the identifier.

Privacy

The calculation and batch audit run in the browser. Saving recent checks uses browser-local storage. A portable link puts the current single-input state in its URL hash, so only share that link when the identifier is appropriate to disclose.