What this calculator works out
This calculator estimates the printed width of a linear barcode from the number of characters, the width each character occupies, and the quiet zones at either end.
It is a generic planning estimate. Standard retail symbologies such as EAN-13 and UPC-A have exact published dimensions, and those take precedence over any calculation.
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Before you size a label
- For retail products, use the published dimensions. EAN-13 at 100% magnification is 37.29 mm wide including quiet zones, and 25.93 mm high.
- Quiet zones are mandatory clear space either side. For EAN-13 that is 3.63 mm on the left and 2.31 mm on the right — omitting them is the most common cause of scan failure.
- Width per character depends on the symbology and the module width. Code 128 packs more densely than Code 39.
- Retail symbols may be scaled between roughly 80% and 200% of nominal, but not stretched in one direction only.
A scanner needs clear space before and after the bars to recognise where the symbol begins and ends. Designers routinely crowd them with text or graphics because the space looks empty, and the result is a code that fails at the till. The quiet zone is not a margin — it is part of the symbol.
How this calculator works
Character width plus quiet zones:
Width = characters × width per character + (2 × quiet zone)Treating every character as the same width is a simplification. Real symbologies include start and stop patterns, check digits and guard bars that are not characters, which is why the published nominal dimensions differ from this estimate.
Use this to plan label space early. Confirm against the symbology's specification before going to print.
Worked example: thirteen characters
Using the default figures — 13 characters at 1.02 mm each with 6.4 mm quiet zones:
- Width: 13.26 + 12.8 = 26.06 mm
Worth comparing that against reality. A genuine EAN-13 at 100% magnification is 37.29 mm wide including its quiet zones — around 40% wider, because the symbol carries guard bars and a check digit beyond its thirteen digits. That gap is exactly why this tool is a planning estimate: it will tell you whether a label is roughly the right size, and the specification will tell you whether it works.
Common mistakes
- Omitting or crowding the quiet zones. The commonest cause of scanning failure.
- Scaling below the symbology's minimum. Retail symbols have a defined lower limit.
- Stretching in one direction. Symbols must be scaled proportionally.
- Printing light bars on a dark background. Scanners expect dark bars on light.
- Using red for the bars. Many scanners use red light and cannot distinguish them.
Frequently asked questions
How do I get a real barcode for a product?
Retail barcodes use GS1 numbering, and a company prefix is obtained by joining GS1 in your country. Numbers bought cheaply from resellers are often reassigned older prefixes, which many retailers will not accept. If products are to be sold through supermarkets or major retailers, going through GS1 directly is generally required.
What size can a barcode be?
EAN-13 may be reproduced between 80% and 200% of its nominal size, giving a width from roughly 30 mm to 75 mm. Below 80% scanning reliability falls, and many retailers will reject undersized symbols. The height should not be truncated either — cutting it reduces the number of angles at which a scanner can read it.
Which symbology should I use?
EAN-13 or UPC-A for retail products. Code 128 for logistics and internal use, since it is compact and encodes the full character set. Code 39 where simplicity matters more than density. ITF-14 for outer cases. The application generally dictates the choice rather than the other way round.
Why does my barcode not scan?
In rough order of frequency: insufficient quiet zone, poor print contrast, the symbol scaled too small, ink spread on absorbent material, a damaged or curved surface, or the wrong colours. Printing a test at final size on the final material and scanning it is worth doing before any print run.
Is what I enter stored?
No. Figures are processed in your browser and never transmitted or retained.
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References
- GOV.UK — product labelling requirements and trading standards
- MoneyHelper — guidance for small businesses on setup costs
Sources are checked at publication and can change — how I choose and check references.