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Code 128 vs. EAN-13 vs. UPC-A: Choosing a Barcode Format
Start with the system that will read the label. A bin code such as WH-BIN-042A and a product sold at checkout answer different questions, even if both labels print on the same machine.
Quick comparison
| Format | Data | Length | Typical use |
|---|---|---|---|
| Code 128 | ASCII letters, digits and symbols | Variable | Bins, equipment and internal SKUs |
| EAN-13 | Digits | 13 including check digit | Retail product carrying a GTIN-13 |
| UPC-A | Digits | 12 including check digit | Retail product carrying a GTIN-12 |
| Code 39 | A–Z, digits, space and -. $/+% | Variable | Legacy systems or a specified label format |
Code 128 for an internal label
Encode the inventory key exactly as the receiving software stores it. Lowercase letters and punctuation are allowed. Code Set C packs pairs of digits compactly; a long SKU with letters may need more print width than an equally long numeric value. The encoder adds a modulo-103 check character: do not append it to the SKU.
General Code 128 is not interchangeable with GS1-128, which has additional rules for application identifiers and separators. If a customer specifies GS1-128, confirm the full label requirement before sending a carton.
UPC-A and EAN-13 at checkout
Use the identifier assigned to that trade item. UPC-A contains 11 data digits and a check digit; EAN-13 contains 12 data digits and a check digit. A scanner may return a UPC with an extra leading zero when configured for EAN-13 output. Check the receiving software before changing your database keys.
When Code 39 is required
Standard Code 39 works well for a legacy reader configured for uppercase tags. A modulo-43 check character is optional in the symbology but may be required by your customer. Do not silently uppercase a case-sensitive SKU to make it fit; ask which string is expected.
Worked example: check an EAN-13
Using the sample base 400638133393, multiply the digits alternately by 1 and 3 from the left. The weighted total is 89. The next multiple of 10 is 90, so the last digit is 1: 4006381333931. If the total is already a multiple of 10, the digit is 0.
Reference: GS1 · Check digit calculator