Interleaved 2 of 5
Published by the QRinsec Editorial Team — practical documentation about QR codes, barcode standards, and QRinsec’s client-side tools. Content is reviewed against product testing and published technical documentation from sources such as GS1, Denso Wave, and ISO standards where applicable.
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Interleaved 2 of 5 (ITF) is a numeric-only, high-density 1D barcode that always encodes an even number of digits.
Important Notice
ITF encodes pairs of digits — an odd number of digits must be padded with a leading zero.
Important Notice
Bearer bars are mandatory for GS1 ITF-14 on corrugated cardboard; omitting them causes scan failures.
Key Facts
- Characters
- Numeric only (0–9)
- Length
- Variable (even digits only)
- Check Digit
- Optional (Mod 10 required for ITF-14)
- Standard
- ISO/IEC 16390
- Common Use
- Warehousing / ITF-14 cartons
What is Interleaved 2 of 5?
Interleaved 2 of 5 (ITF, also I 2/5) is a numeric-only linear barcode symbology standardised in ISO/IEC 16390. Introduced by Computer Identics in 1972, it encodes pairs of digits simultaneously — one digit in the bars and the adjacent digit in the spaces between them, hence 'interleaved'. This technique achieves roughly double the data density of standard 2 of 5 barcodes. ITF is the underlying symbology for ITF-14 (GTIN-14 on corrugated cases), but ITF itself can encode any even number of digits.
Symbol structure explained
ITF encodes digits in pairs. Each character pair is represented by 5 bars and 5 spaces, with 2 of the 5 elements being wide ('2 of 5'). Bars encode the first digit of the pair; spaces encode the second. The symbol begins with a narrow bar start pattern and ends with a wide bar/narrow bar/wide bar stop pattern. Because digits are interleaved, the total number of digits must always be even — an odd digit count requires a leading zero pad.
Optional check digit (Modulo 10)
ITF has no mandatory check digit in the base standard, but a Modulo 10 check digit is required when used as ITF-14 (GS1 specification). The same Modulo 10 algorithm used in EAN/UPC applies:
- Multiply odd-position digits by 3, even-position digits by 1.
- Sum all products.
- Check digit = (10 − (sum mod 10)) mod 10.
ITF vs. ITF-14 vs. Code 128
ITF is the generic symbology; ITF-14 is a specific GS1 application of ITF always encoding exactly 14 digits (GTIN-14) with mandatory bearer bars on corrugated packaging. Code 128 supports alphanumeric data and variable length but is slightly less dense than ITF for purely numeric data. ITF is the most space-efficient numeric-only linear barcode.
When to use ITF
ITF is appropriate for:
- Numeric-only data where maximum linear density is required.
- Warehouse and distribution centre labels.
- ITF-14 (GS1) carton-level identification on corrugated cardboard.
- Legacy systems that specify ITF.
For variable-length or alphanumeric data, use Code 128 instead.
Printing requirements
Minimum X-dimension: 0.191 mm (general); 0.635 mm (GS1 ITF-14). Wide-to-narrow ratio: 2:1 to 3:1 (2.5:1 optimal). Quiet zones: 10× X-dimension each side. Bearer bars (horizontal rules top and bottom) are mandatory for ITF-14 on corrugated; optional but recommended for all ITF on corrugated substrates.
Common scanning failures
The interleaved structure means that a single misread bar or space affects two digits simultaneously — double the impact of an error compared to non-interleaved codes. Correct wide-to-narrow ratio is critical; bar width deviation > ±20% causes systematic misreads. On corrugated cardboard, always use bearer bars to prevent flute-line false positives.
Comparison
| Feature | ITF | ITF-14 (GS1) | Code 128C |
|---|---|---|---|
| Data Type | Numeric only | 14-digit GTIN-14 | Numeric pairs |
| Length | Variable (even) | Fixed 14 digits | Variable |
| Check Digit | Optional | Mandatory (Mod 10) | Mandatory (Mod 103) |
| Bearer Bars | Optional | Mandatory (corrugated) | Not used |
Frequently Asked Questions
What is the difference between ITF and ITF-14?
ITF (Interleaved 2 of 5) is the general-purpose numeric symbology that can encode any even number of digits. ITF-14 is a specific GS1 application of ITF that always encodes exactly 14 digits (GTIN-14) and requires mandatory bearer bars on corrugated packaging.
Why must ITF encode an even number of digits?
Because ITF interleaves two digits at a time (one in bars, one in spaces), it cannot encode an odd number of digits. If your data has an odd count, pad with a leading zero.
Is ITF numeric only?
Yes. ITF encodes only digits 0–9. For alphanumeric data, use Code 128 or another full-character symbology.
Do ITF barcodes need a check digit?
Not in the base standard. However, GS1 ITF-14 mandates a Modulo 10 check digit as the 14th digit. Some industry applications also require a check digit — always verify with the receiving system's specification.
Can ITF be printed directly on corrugated cardboard?
Yes, and it is well-suited for this substrate due to its wide minimum X-dimension tolerance. Bearer bars (horizontal lines top and bottom) are strongly recommended on corrugated to prevent the flute pattern from being misread as barcode bars.
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