Standard 2 of 5

Standard 2 of 5 is a low-density numeric barcode symbology dating back to the 1960s, historically used in photofinishing, warehouse sorting, and sequential airline ticket numbering.

Standard 2 of 5 is a low-density numeric symbology that has been in use since the 1960s. It has been applied in the photofinishing and warehouse sorting industries, as well as for sequentially numbering airline tickets. The symbology is called "2 of 5" because digits are encoded with 5 bars, 2 of which are always wide (the remaining three are narrow). Standard 2 of 5 is a numeric symbology, and its character set includes the 10 digits (0, 1, 2, 3, 4, 5, 6, 7, 8, 9).

Standard 2 of 5 is a very simple symbology in that all encoding information is contained in the width of the bars. The spaces in the barcode exist only to separate the bars themselves. A bar may be either wide or narrow, with a wide bar generally three times as wide as a narrow bar. The exact size of the spaces is not critical, but is generally the same width as a narrow bar.

The symbology gets its name because every character is encoded with 5 bars, 2 of which are wide. Standard 2 of 5 uses only bar width to encode data. Interleaved 2 of 5, by contrast, uses the widths of both bars and spaces.

A complete Standard 2 of 5 barcode must include a start character and a stop character. Optionally, it ends with a modulo-10 check digit.

Standard 2 of 5 is a very simple, low-density symbology. Its variant, Interleaved 2 of 5 (ITF25), offers a somewhat higher density.

Standard 2 of 5 is also known as Code 25.

• Industry 2 of 5 — Identical to Standard 2 of 5.
• Standard 2 of 5 Mod 10 — A modulo-10 check digit is appended to the barcode message to perform validation.

A typical Standard 2 of 5 barcode has the following structure:

1. A start character
2. The encoded message
3. An optional Mod 10 check digit
4. A stop character

1. Starting with the rightmost digit in the message, mark each character with an even or odd position. The rightmost digit has the even position.
2. Sum all digits in the odd position.
3. Sum all digits in the even position, then multiply by 3.
4. Add the results of steps 2 and 3.
5. Divide the result of step 4 by 10; the check digit is the value equal to 10 minus the remainder.

"Industrial 2 of 5" is another name for "Standard 2 of 5" and is functionally identical to it.