Code 128 generator

Three code sets inside one barcode

Every symbol is a value from 0 to 102, and what that value means depends on the code set in force. Switching costs one extra symbol, so the shortest barcode depends on your text.

The three code sets inside Code 128

Code set	Holds	One symbol carries
A	Capitals, digits, punctuation, control codes	1 character
B	Capitals, lowercase, digits, punctuation	1 character
C	Digit pairs from 00 to 99	2 digits

The number 123456789012 goes straight to set C and takes 6 data symbols. Add the start, check and stop and the whole thing is 101 modules, or 39.93 mm with clear space at a 0.33 mm narrow bar. Your text may need a mix. BIN-A14-0072 stays in set B for the letters, then switches to set C for the final 0072. The route table shows that switch when you type it.

The check character, worked through

A scanner adds up the symbols, each multiplied by its position, then divides by 103. The remainder must match the check character. Here is the published example for PJJ123C with Start A, which has value 103.

The check character for BIN-A14-0072, worked through

Symbol	Value	Position	Product
Start A	103	1	103
P	48	1	48
J	42	2	84
J	42	3	126
1	17	4	68
2	18	5	90
3	19	6	114
C	35	7	245

The products total 878, and 878 divided by 103 leaves 54. This generator starts the same text in set B, whose start value is 104, so its total is 879 and its check value is 55. Both are valid. The route table for your own text uses the same steps.

Sizes and clear space

Code 128 has no single required size, because labels range from jewelry tags to pallet sheets. The standard asks for 10 modules of clear space on each side, and the file includes it. GS1 sets its own sizes only for GS1-128 in the supply chain.

Code 128 sizes and the width of the sample with its clear space

Narrow bar	Good for	BIN-A14-0072 with clear space
0.25 mm	Small labels at 300 dpi or higher	1.73 in (44 mm)
0.33 mm	Most stock and bin labels	2.29 in (58.08 mm)
0.508 mm	Labels scanned from a distance	3.52 in (89.41 mm)

Height is your choice too. Taller bars give a hand scanner more room to be off level, and 15 mm is a comfortable start. Bars do not need to fill the label. Leaving white space around them does more good.

Tab and Enter after the scan

Adding a key press saves a step when you scan into a form. With Tab, each scan moves to the next field, and with Enter, the form submits by itself. The key goes in the barcode using set A's control codes, so it works with any scanner in keyboard mode. It does not print under the bars.

Where Code 128 fits

It suits your own labels because it is compact and holds both letters and digits. If you need a whole list of stock codes, the SKU generator builds them and draws each one in Code 128. If a system insists on the older format, use the Code 39 generator. Every other format, from UPC to Data Matrix, is in the barcode generator, and a product sold at a checkout gets its retail symbol from the UPC generator. ISO sells the Code 128 standard as a paid document. The open references listed at the end are the Wikipedia entry and the GS1 specification. Long text or small parts suit a Data Matrix code, which fits far more in less space. Cartons going out to customers usually need an ITF-14 or GS1-128.

Code 128 in Word and Excel

A plain barcode font cannot make a Code 128 label on its own. That is because the symbol ends in a computed check character and switches between three character sets. The guides to making a barcode in Excel and in Word explain what each program can do by itself. They also say when a file from this tool is the simpler route.