Code 39 Barcode FAQ

Code 39 barcode symbols shall comprise the following parts:

1. leading quiet zone
2. start character
3. code 39 character set with check digit, if used
4. stop character
5. trailing quiet zone

Note: characters are separated by a space (the intercharacter gap).

Start/Stop Characters

Code 39 uses asterisk character (*) as Start and Stop characters, and it should not be part of the Code 39 barcode data. In the barcode Human-readable interpretation, it can display or hide start/stop characters (asterisk *).

Example: Code 39 barcode with start/stop displayed

Code 39 barcode standard mode supports 43 characters, including

• Numeric digit: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9
• Uppercase letters (A - Z)
• Special characters: - (Dash), $ (Dollar), % (Percentage), (Space), . (Point), / (Slash), + (Plus)
• Start/Stop character

Code 39 Full ASCII

Code 39 supports encoding the full 128 character ASCII character set in accordance with ISO 646 IRV.

In full ASCII code 39 symbols, regular mode supported chars (0-9, A-Z, ".", "-" and space) are the same as their representations in Code 39. Lower case letters, additional punctuation characters and control characters are represented by sequences of two characters of Code 39.

Table-1: Encode the Full ASCII character set in Code 39

How many characters in a Code 39 barcode?

• Code 39 standard mode: it supports 43 characters.
• Code 39 Full ASCII mode: it supports 128 characters.

What is the Code 39 barcode minimum length?

There are no rigid requirements for Code 39 barcode data size.

Some barcode scanners will not scan code 39 for less than 4 characters by default. You need configure barcode scanner settings to minimize the length of code 39 characters to 0.

Code 39 does not include a checksum or check digit by default. For applications requiring enhanced data security, the modulo 43 (MOD43) check character may be used as a check digit.

How to calculate Code 39 check digit?

When a checksum or check digit is included in the Code 39 barcode, the following check character algorithm (MOD43) should be used.

1. Each data character is assigned a numerical value as shown in Table-1 below
2. Calculate the sum of the numerical values for all the data characters of a symbol
3. Divide this sum by 43.
4. The character whose value (from Table-1) is the remainder from the division in step 3) is used as the check character.

For example, calculate the check character for Code 39 data "CODE 39"

1. All 7 chars character values are 12, 24, 13, 14, 38, 3 and 9
2. Sum of the values is 113
3. Divid by 43: 113/43= 2 with remainder 27
4. Character value 27 is "R"
5. The calculated check digit is "R"
6. The complete Code 39 data with checksum is "CODE 39R"

Table-2: Code 39 numerical character values for modulo 43 check

Code 39 barcode text label is also known as human-readable interpretation. It should normally be printed with the Code 39 symbol.

A sample Code 39 image without human-readable interpretation printed.



Code 39 start/stop characters my be printed. A sample Code 39 image without start/stop characters printed.

Code 39 barcode uses the following dimension settings:

• Width of narrow element (X): the mimumum bar width is defined by the application specification
• Wide/narrow ratio (N): the valid value is from 2.0 to 3.0 inclusive.
• Width of intercharacter gap (I):
  • minimum gap is equal to X
  • maximum: for X < 0.287mm, is 5.3X; for X >= 0.287mm, is 1.52mm or 3X, whichever is greater.
• Quiet zone: the minimum width of quiet zone is 10X.
• Bar code height: the minimum height is 5.0mm or 15% of symbol width (excluding quiet zones), whichever is greater.

Code 39 barcode dimension size calculator

The width of a Code 39 barcode, including quiet zones, can be calculated from the following expression:

W = (C + 2)(3N + 6) X + (C +1) I + 2Q

where

• W: is the barcode width
• C: is the number of Code 39 data characters (including the check digit if used)
• N: is the width/narrow ratio
• X: is the width of a narrow element
• I: is the width of the intercharacter gap
• Q: is the width of the quiet zone

To be scannable by barcode scanner device or barcode reader software, you need follow the guide in the barcode specification. Here are some:

• Code 39 wide/narow bar ratio should be 2.0 and 3.0
• The minium of intercharacter gap is equal to bar width
• Minium width of quite zone should be equal or greater than 10 * bar width

OnBarcode provides several barcode reading solutions for you.

• Free Code 39 Barcode Scanner Software: you can use the free Windows software to read, scan code 39 data from the image files.
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