Data Matrix generator

How much a Data Matrix holds

Capacity jumps in steps, because the code can only be certain sizes. These limits are what the tool itself holds, measured one character at a time. Digits pack tightest, because the code stores them in pairs. Capitals come next, and bytes such as accented letters take the most room.

Square Data Matrix sizes and what each holds

Modules	Digits	Capitals	Bytes
10 x 10	6	3	1
12 x 12	10	6	3
16 x 16	24	16	10
18 x 18	36	25	16
24 x 24	72	52	34
32 x 32	124	91	60
48 x 48	348	259	172
88 x 88	1,152	862	574
144 x 144	3,116	2,335	1,556

Rectangles suit narrow places such as the edge of a board, but they top out early:

Rectangular Data Matrix sizes and what each holds

Rectangle	Digits	Capitals	Bytes
8 x 18	10	6	3
8 x 32	20	13	8
12 x 36	44	31	20
16 x 48	98	72	47

Module size and print size

The size of the whole code is modules times module size. The sample text, PN 88421 REV C SN 000731, is 24 characters and comes out at 18 x 18 modules. With a 0.495 mm module, that is 8.91 mm across, or 9.9 mm counting clear space.

GS1 sets a range for codes on trade items. For a code scanned at a retail checkout it is 0.396 mm to 0.990 mm with a 0.495 mm target. For a code that only carries a web address for shoppers it is 0.396 mm to 0.743 mm. For general distribution it is 0.743 mm to 1.5 mm. Outside GS1 use you can go smaller, as long as your printer and scanner can cope. Under about 0.25 mm, print a test before you commit.

GS1 mode, without the jargon

GS1 data is written as pairs: a short number that says what comes next, and then the value. Those short numbers are called Application Identifiers. The form builds the string for you and checks your GTIN's last digit.

GS1 application identifiers the GS1 mode accepts

Identifier	What it holds	Example
(01)	GTIN, always 14 digits	(01)09521234543213
(17)	Expiry date as YYMMDD	(17)281231
(10)	Lot or batch, up to 20 characters	(10)L2411A
(21)	Serial number, up to 20 characters	(21)000731

The GTIN must be one your company holds. GS1 does not allow its internal-use ranges in this format, so the form refuses them. For parts and assets of your own, use Any text. Numbers starting with 952 are GS1's own demo range, which is why the sample uses one.

Where the small size pays off

Electronics makers mark circuit boards with Data Matrix, and the Electronic Industries Alliance recommends it for small components, according to Wikipedia. It is also what you want when a QR code will not fit, because its clear space is a quarter as wide.

For long text on a label that a line scanner must read, a PDF417 code is the alternative. If you only need a short code on a stock label, a Code 128 barcode is simpler and a laser scanner can read it. Compare all of them against your own text with the barcode generator.

Getting a clean print

Keep modules square. Stretching the file to fit a space can stop a code reading. Use dark ink on a light background, and leave the 1 module of clear space all the way around. A small module on a 203 dpi printer rounds to few dots. So check the PNG readout, which says what each module becomes at your resolution.

Where Data Matrix sits among 2D codes

Data Matrix and QR Code are read as pictures rather than along a line. PDF417 is a stack of rows that some sweeping line scanners can read. What a 2D barcode is sets out which one suits which job, and why retail checkouts are being upgraded to read them. The GS1 mode produces a GS1 DataMatrix, one of the symbols in the GS1 barcode family.