Code 39 barcode generator

Type capital letters, digits and a few symbols; lowercase is turned into uppercase. Add the optional mod 43 check character if your system expects it.

Code 39 data

A–Z, 0–9 and - . $ / + % and space. Lowercase becomes uppercase.

Add mod 43 check character

58.8 × 23.7 mm printed size, module 0.3 mm.Encodes PART-0042

Need many? Make a batch or a label sheet.

Size and colour

Module width

Bar height

Blank margin

mod.

Show the text

Bars

#000000

Background

#FFFFFF

Transparent

What is Code 39?

Code 39 (also called Code 3 of 9) is one of the oldest alphanumeric barcodes. Each character is drawn on its own, separated by a gap, so it is simple to print and to read, but wider than Code 128 for the same data.

It does not need a check character, but some systems ask for the optional mod 43 one. Turn it on here and it is added to the bars and to the text.

Where it is used

ID badges and membership cards
Part numbers in older industrial systems
Library and inventory systems that were set up for Code 39

What it holds

What a Code 39 barcode holds
	Code 39
Characters	A–Z, 0–9, space and - . $ / + %
Length	Variable; this site takes up to 43 characters
Check character	Optional, mod 43
Start and stop	An asterisk at each end, added by the encoder

Printing Code 39 barcodes

If you are starting a new system, Code 128 holds more characters in less space.
Match the check character setting to what your scanner or software expects.
Keep the blank margin on both sides.
Print one sample on the printer and label stock you will use, and scan it with the scanners that have to read it, before a full run.

Need a sheet of them? The batch generator makes up to 1,000 Code 39 barcodes at once and lays them out on Letter or A4 label sheets.

Questions about Code 39

Why are the asterisks shown under the bars?

Code 39 starts and stops with the * character. Many printers show it in the text; the scanner does not send it to your software.

How is the mod 43 check character worked out?

Each Code 39 character has a value from 0 to 42 (0–9, then A–Z, then - . space $ / + %). Add the values of the data, divide by 43 and take the remainder: the character with that value is the check character.

Can Code 39 carry lowercase letters?

Not directly. An extended mode uses pairs of characters for lowercase, but scanners must be set up for it. This generator keeps to standard Code 39 and turns lowercase into uppercase.

Sources

bwip-js
The open-source library that draws the barcodes on this site (MIT licence).