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Category Graphic Generators

Numeric Data (even length) Enter an even number of digits (0–9). Pairs are encoded as Code 128-C symbols.

Scale (px/module)

Bar Height (px)

Bar Color

Background

Show text below barcode

Presets:

Enter numeric data and click Generate

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About

Code 128-C is the numeric-only subset of the Code 128 symbology defined in ISO/IEC 15417. It encodes digit pairs (00 - 99) into single symbols, achieving roughly double the density of Code 128-A or 128-B for purely numeric data. This makes it the mandatory encoding for GS1-128 application identifiers, SSCC-18 shipping labels, and any logistics context where an odd digit count or a misplaced character causes scanner rejection at the packing line. The checksum is a weighted modulo-103 sum. A single transposition in the input will produce a valid-looking but semantically wrong barcode. This tool computes the check digit, renders the barcode to spec, and flags input errors before they reach a printer.

Limitations: Code 128-C accepts even-length numeric strings only. If your data contains letters or an odd digit count, you need Code 128-A/B or a mixed-mode encoder. The quiet zone on each side must be at least 10 modules wide per ISO/IEC 15417 §4.3.2.1. This generator enforces that automatically.

Formulas

The Code 128-C check digit is computed as a weighted modulo-103 sum over all encoded symbol values:

C = ( v_start + n∑i=1 i × v_i ) mod 103

Where v_start = 105 (the fixed Start C symbol value), n is the number of data symbols (digit pairs), i is the 1-based position index, and v_i is the numeric value of the i-th digit pair (00 - 99). The resulting C is looked up in the same 103-symbol encoding table and inserted before the Stop pattern.

Total barcode module width: W = 11 × ( 1 + n + 1 ) + 13 + 2 × Q, where the first 1 is Start C, the second 1 is the check symbol, 13 is the Stop pattern width, and Q ≥ 10 modules is each quiet zone.

Reference Data

Value	Digit Pair	Bar Pattern (B S B S B S)	Module Widths
0	00	212222	11
1	01	222122	11
2	02	222221	11
3	03	121223	11
4	04	121322	11
5	05	131222	11
6	06	122213	11
7	07	122312	11
8	08	132212	11
9	09	221213	11
10	10	221312	11
20	20	231212	11
30	30	112232	11
40	40	122132	11
50	50	122231	11
60	60	113222	11
70	70	123122	11
80	80	123221	11
90	90	223211	11
99	99	231211	11
103	Start C	211232	11
106	Stop	2331112	13

Frequently Asked Questions

Code 128-C encodes data in pairs. Each symbol represents a two-digit value from 00 to 99. An odd-length input leaves one digit unpaired. In production, mixed-mode encoders switch to Code 128-A or 128-B for the trailing digit, but a pure 128-C encoder must reject odd-length input to maintain data integrity.

The check digit uses a positional weighting scheme: each symbol value is multiplied by its 1-based position index before summing modulo 103. This catches single-symbol errors and most transposition errors. A scanner verifies the checksum on decode; if it fails, the barcode is rejected rather than returning corrupted data.

The standard specifies a minimum quiet zone of 10 times the module width (the narrowest bar) on each side of the barcode. This generator automatically adds compliant quiet zones. If you crop the image manually, ensure you preserve at least 10× the module width, or scanners may fail to detect the start/stop patterns.

No. Code 128-C is strictly numeric (digit pairs 00 - 99). For alphanumeric data, use Code 128-A (uppercase + control characters) or Code 128-B (full ASCII printable range). GS1-128 labels typically use Code 128-C for the numeric Application Identifier portion and switch subsets for any alpha segments.

ISO/IEC 15417 recommends a minimum X-dimension (module width) of 0.191 mm for open-system applications. For retail and logistics, 0.250 - 0.330 mm is standard. In this generator, module width is controlled by the Scale setting. At scale 2, each module is 2 px, suitable for screen display. For print at 300 DPI, use scale 3 - 4.

Yes. The recommended minimum height is 15% of the barcode width or 6.35 mm, whichever is greater (per GS1 General Specifications). Shorter bars reduce the scanner's vertical capture window, especially for handheld laser scanners that sweep at an angle. This tool defaults to 80 px bar height, which satisfies the ratio for typical data lengths.