How to use this calculator
Start with the deterministic fixture values already shown, then replace each input with measurements from your job. Use consistent units and review the highlighted assumptions before using the result in purchasing or production.
Formula and method
UPC-A uses the GS1 modulo-10 method. From the rightmost body digit, alternating weights 3 and 1 are applied before the final digit completes a multiple of ten.
Worked example
UPC-A body 03600029145 has check digit 2, producing the complete number 036000291452.
How to interpret the result
Use validation to catch many typing errors before creating or checking a UPC-A symbol. Preserve leading zeros.
UPC-A and a 14-digit GTIN field
UPC-A carries a 12-digit GTIN-12. Systems that require a uniform 14-digit GTIN field represent the same identifier by adding two leading filler zeros; for example, 036000291452 becomes 00036000291452.
Removing leading zeros from an arbitrary GTIN-14 is not a general conversion to UPC-A. The reverse is only unambiguous when the 14-digit value is a zero-padded GTIN-12 representation.
Limitations
Checksum validity does not establish that a UPC was licensed, assigned to the stated product or encoded with compliant dimensions.
Primary references
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