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Free Code 39 barcode generator.

Code 39 encodes capitals, digits, space and six symbols in a linear barcode, as on Odette transport labels and US military shipping labels. Enter your data and download the barcode.

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Code 39 barcode encoding ABC-1234 — Example: ABC-1234 framed by the * start and stop characters, 159 modules at a 3:1 ratio

How to create a Code 39 barcode

01
Type the value as your label specification defines it

Start with the data identifier (DI) if your label uses one, as in P1234567 for a part number on Odette labels; MIL-STD-129R shipping labels use none. Leave out the asterisks; type any required mod 43 check character last.
02
Set the module width in pixels, not millimetres

Set Resolution (dpi) to your printer's and Module width to Pixel, so narrow and wide elements cover whole dots and keep an exact 3:1. At 300 dpi, 4 px is 0.3387 mm, inside Odette's 0.33–0.43 mm.
03
Download PNG and keep the margins blank

Download PNG and place it at 100%. The image has no quiet zone, so keep at least 6.4 mm blank per side on Odette labels, otherwise 10 modules and at least 6.35 mm (TEC-IT).

Code 39: capitals, digits and symbols in a self-checking barcode

Code 39, also called Code 3 of 9, is a linear barcode for 43 characters: 0–9, A–Z, space and - . $ / + %. Every character has nine bars and spaces, three of them wide, and an asterisk marks start and stop. ISO/IEC 16388 specifies the symbology. Use it where a label specification names it: Odette OTL 1 transport labels, US military shipping labels and IBM's LTO tape labels. For codes of your own, Code 128 is more compact.

Where Code 39 is printed: automotive, defence, tape libraries

Courier in a navy cap lifting a labelled carton out of a delivery van

TEC-IT's Odette OTL 1, VDA 4902 and AIAG B-10 templates give each bar-coded field its own Code 39. A data identifier leads the data: P for the part number, Q for the quantity, V for the supplier. SEG Automotive's 2018 supplier manual asks for Code 39 to ISO/IEC 16388 on all barcodes unless agreed otherwise.

Military shipping labels under MIL-STD-129R carry three Code 39 symbols, among them the 17-character transportation control number (TCN). IBM's LTO label gives tape libraries six volume-serial characters and a media type such as L9 in Code 39. Health Industry Bar Code (HIBC) supplier labels may use Code 39, always with a mod 43 check character.

A print defect causes a no-read, not a wrong part number

ABC-1234 in Code 39 to scale: 159 modules of 0.33 mm at 3:1, 13 mm bars, 6.4 mm quiet zones

Every Code 39 character has exactly three wide elements out of nine. If a spot or void changes one element, no valid character remains and the scanner reports no read. A misread needs two aligned defects in one character, according to MIL-STD-1189B, the US defence standard for Code 39 until 1997.

At a module width of 0.33 mm, Odette lets each bar and space deviate by 0.11 mm, more than one dot of a 300 dpi printer. The price is width: 16 modules per character at 3:1, so ABC-1234 needs 159 modules, 52.5 mm of bars at 0.33 mm.

Image formats online; mod 43, other ratios and series in TEC-IT software

Engineer at a machine test cell holding up a printed linear barcode label

The online generator draws Code 39 at a 3:1 ratio, without a check character. It downloads GIF, PNG and JPG for free, and SVG and higher-resolution images with a plan. Guests create one Code 39 per download; signed in for free, you can turn a whole list in a data sheet into codes.

TBarCode SDK and Barcode Studio can add the mod 43 character automatically and set other ratios, such as the 2.75:1 of IBM's LTO label. Barcode Studio imports CSV lists or counts up serial numbers, such as a run of LTO volume serials; TBarCode Office updates a Code 39 when its Excel cell changes.

Code 39 at a glance

Type: Linear (1D), discrete, self-checking, bidirectional, variable length
Specification: ISO/IEC 16388:2023; USS Code 39 is the same symbology
Character set: 0–9, A–Z, space, - . $ / + % (43); * for start and stop
Symbol character: 9 elements, 3 of them wide; 15 modules at 3:1, plus a 1-module gap
Wide-to-narrow ratio: 3:1 in the online generator; Odette 2.8–3.2, MIL-STD-130N 2.1–3.1
Check character: Optional, modulo 43; none by default
Module width (X): At least 0.19 mm (TEC-IT); Odette 0.33–0.43 mm
Quiet zone: 10X, at least 6.35 mm (TEC-IT); Odette at least 6.4 mm
Bar height: At least 15% of the symbol length and 6.3 mm (TEC-IT)

How ABC-1234 is built, and its mod 43 check character

Framed by the start and stop character *, ABC-1234 becomes ten characters of 15 modules, with a one-module gap between them: 10 × 15 + 9 = 159 modules.

For the optional check character, add the character values: digits count 0–9, A–Z 10–35, and - . space $ / + % 36–42.

Character	A	B	C	-	1	2	3	4	Sum
Value	10	11	12	36	1	2	3	4	79

79 divided by 43 leaves 36, the value of the hyphen: with its check character the data reads ABC-1234-, eleven characters and 175 modules.

Code 39 print settings by label specification

Specification	X (narrow element)	Wide : narrow	Bar height	Quiet zone	Minimum grade (ISO/IEC 15416)
Odette OTL 1 label	0.33–0.43 mm	3:1 (2.8–3.2)	13 mm	≥ 6.4 mm	C at the customer
MIL-STD-129R shipping label	≥ 0.25 mm (0.010 in)	3:1 (2.4–3.2)	≥ 12.7 mm	≥ 6.35 mm	2.5 (B) at production
MIL-STD-130N item marking	0.19–0.38 mm	2.1–3.1	not given	not given	3.0
HIBC labels (HIBCC)	0.25 mm, ≥ 0.17 mm	not given	≥ 15% of length	≥ 10X	C; aim for B
IBM LTO label	0.432 mm	2.75	≥ 11.1 mm	≥ 10X (4.32 mm)	C

Whole printer dots. On a 203 dpi printer, 3 dots give X = 0.375 mm and 9-dot wide bars, inside Odette's range and above MIL-STD-129R's minimum.
Height. Make the bars at least 15% as high as the symbol is long. Odette fixes 13 mm and therefore asks to keep codes over 13 characters to a minimum.
Text line. Odette leaves the DI out of the human-readable characters and prints it beside the field title. Switch off Show human-readable text and place the value in your layout.

Code 39 mistakes and their fixes

Lower case in plain Code 39. The generator shows “Input data contains unsupported characters” instead of a barcode. Write capitals, or use Full ASCII where every reader is set to it.
Full ASCII on labels for partners. A reader not in Full ASCII mode outputs a as +A. Use plain Code 39 there: MIL-STD-129R even allows only A–Z, 0–9 and $, IBM's LTO label only A–Z and 0–9.
Millimetre widths off the printer grid. At 300 dpi, 0.33 mm is 3.9 dots, so the generator draws narrow bars and spaces 3 or 4 pixels wide. Enter the module width in pixels.
A lost space check character. The mod 43 character of ABC-1236 is a space (value 38), and software that trims trailing spaces deletes it. If it must be stored, HIBCC asks for an explicit ASCII 32.

When another linear barcode fits better

Code 128 ›

Full ASCII without pairs, a mandatory check character and 112 modules for ABC-1234 instead of 159: the better choice for your own data.

Code 93 ›

The same 43 characters, denser, with two check characters (modulo 47) added automatically.

Interleaved 2 of 5 ›

Digits only, in pairs, so the count must be even. Shorter than Code 39 for numeric serial numbers; one letter rules it out.

Code 11 ›

Digits and the hyphen, mainly for marking telecommunications equipment. Not self-checking: TEC-IT's reference recommends two check digits.

Code 32 ›

The Italian Pharmacode: a nine-digit number converted into six Code 39 characters. Use it only where that code is required.

Code 39 or Code 39 Full ASCII

Both use the same bars and asterisks. Full ASCII writes the characters plain Code 39 lacks as pairs, which only readers in Full ASCII mode convert back.

Code 39

The standard's 43 characters: capitals, digits, space and - . $ / + %. Choose it for any label that partners scan.

Create Code 39 ›

Code 39 Full ASCII

Also called Code 39 Extended, it encodes all 128 ASCII characters: a becomes +A, and a tab, typed as \t with Escape sequences on, becomes $I. Letters outside ASCII, such as ä, are rejected.

Create Code 39 Full ASCII ›

Frequently asked questions

Learn more about Code 39.

Which characters can a Code 39 barcode encode?

The digits 0–9, the capitals A–Z, space and - . $ / + %, 43 characters in all; the asterisk only marks start and stop. Code 39 Full ASCII adds lower case, punctuation and control characters as pairs, such as +A for a.

Does Code 39 need a check digit?

Only where your label format requires one, as HIBC supplier labels do. Code 39 checks itself, and its modulo 43 check character is optional. The online generator adds none: for ABC-1234 it is a hyphen, typed at the end as ABC-1234-.

Do I have to type the asterisks?

No: the generator adds the start and stop character * itself and removes asterisks you type at the beginning or end of the data. The text line under the bars shows your data without them. TEC-IT's barcode software adds them automatically as well.

Why does my scanner show +A instead of a lower-case a?

The barcode is Code 39 Full ASCII, but the scanner reads it as plain Code 39. Full ASCII stores a as the pair +A, and only a reader set to Full ASCII mode turns the pair back into a. Switch that mode on, or encode capitals in plain Code 39.

Is Code 39 allowed for US military item unique identification (IUID)?

Not for the unique item identifier: DFARS 252.211-7003 requires a Data Matrix ECC 200 symbol. MIL-STD-130N accepts Code 39 to ISO/IEC 16388 at a 2.1:1 to 3.1:1 ratio, but prefers Data Matrix even for items outside IUID. MIL-STD-129R shipping labels still carry three Code 39 symbols.

How long can a Code 39 barcode be?

There is no fixed length; width sets the limit, at 16 modules per character with a 3:1 ratio. Twenty characters at 0.33 mm need 351 modules, 115.8 mm before the quiet zones. By the 15% rule, their bars should be at least 17.4 mm high.

More resources

Guide

Label standards with Code 39

VDA 4902 AIAG Autoliv Volkswagen GTL Odette LTO Labels Asset Labels

Related barcode generators

Code 93 Code 128 Code 11 Interleaved 2 of 5 Code 32 All barcode types ›

Free Code 39 barcode generator.

How to create a Code 39 barcode

Type the value as your label specification defines it

Set the module width in pixels, not millimetres

Download PNG and keep the margins blank