Barcode / QR Code Reference
Generate a Code 128 barcode value or check-digit for UPC/EAN, and get specs for common barcode formats.
Inputs
Full encoded value
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Check digit
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Format
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Length
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Specification
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About Barcode / QR Code Reference
UPC check digit math
Sum digits at odd positions × 3, add digits at even positions, take modulo 10. The check digit is (10 - that mod) mod 10. Detects most single-digit and many transposition errors.
Generate the bars
This calculator gives the encoded value and check digit, not the rendered bars. Use a library like JsBarcode or bwip-js to generate actual printable barcode images.
QR vs barcode
Barcodes are 1D (lines), QR is 2D (squares). Barcodes hold 12-128 chars; QR up to 4,296 alphanumeric. QR has built-in error correction; barcodes do not.