Make a Code 39 barcode

Code 39 is one of the oldest general-purpose barcodes. It holds capital letters, digits, space and the symbols - . $ / + %, 43 characters in all, and some older inventory, asset-tag and ID systems still ask for it by name.

Every Code 39 barcode starts and ends with a * character. The page adds both, so type only your own text. A * inside the text is refused, because a scanner would take it for the end.

Lowercase letters are changed to capitals as you type. This page does not use the extended version of Code 39 that spells out lowercase with pairs of characters, so anything outside the 43 characters is refused with a message that names it.

The optional check character

• Code 39 does not need one, but some systems ask for it. Tick Add check character and the page adds one character, worked out by giving every character a value (0 to 9, then A to Z as 10 to 35, then - . space $ / + % as 36 to 42), adding the values and dividing the total by 43. The remainder is the value of the check character.
• HELLO adds up to 17+14+21+21+24 = 97. 97 divided by 43 leaves 11, which is the letter B, so the barcode carries HELLOB. The extra B is shown under the bars, and the system reading it has to expect it.

Wider than Code 128

• Each Code 39 character takes more room than a Code 128 character, so the same text makes a wider barcode. When no one asks for Code 39, the Code 128 barcode generator gives a shorter barcode for the same text.