What this calculator works out
This calculator gives the printed size of a QR code from its module count, the printed size of each module, and the quiet zone around it.
Unlike the linear barcode estimate, this one matches the specification exactly — a QR code really is a square grid of modules with a defined border.
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Before you size a code
- Module count depends on the version, which depends on how much data you encode. Version 1 is 21 by 21 modules and each version adds 4, so version 4 is 33 by 33 and version 40 is 177 by 177.
- The quiet zone is specified as 4 modules on every side. Reducing it is the most common cause of unreliable scanning.
- A widely used rule of thumb is that the code's width should be at least a tenth of the intended scanning distance.
- Shorter URLs need fewer modules, so a shortened link can allow a physically smaller or more robust code.
QR codes carry one of four error correction levels, from roughly 7% to 30% of the code recoverable if damaged. Higher correction means more modules for the same data, so a larger or denser code — but it survives smudging, curvature and partial obstruction, which is why the level is a print decision rather than a technical detail.
How this calculator works
Modules plus quiet zone, times module size:
Total modules across = data modules + (2 × quiet zone modules)
Printed size = total modules × module size in mmThe quiet zone is counted on both sides, so 4 modules of quiet zone adds 8 modules to the width. The result is a square — QR codes are always square, and any stretched reproduction will fail.
Worked example: a version 4 code
Using the default figures — 33 modules, 0.6 mm each, with a 4-module quiet zone:
- Total modules: 33 + 8 = 41
- Printed size: 24.6 mm square
Just under 25 mm, which at the tenth-of-distance rule suits scanning from around 25 cm — comfortable for a leaflet or a business card. For a poster read from three metres, the same code would need to be around 30 cm square. Sizing a code for the distance it will actually be scanned from is the decision that matters, and it is usually made by whatever space happened to be left in the layout.
Common mistakes
- Reducing or removing the quiet zone. Four modules on every side is the specification.
- Sizing for the layout rather than the scanning distance. A tenth of the distance is the guide.
- Stretching the code. It must remain square.
- Inverting the colours. Light code on dark background fails on many scanners.
- Encoding a long URL. More data means more modules and a denser, less robust code.
Frequently asked questions
How small can a QR code be?
Physically, a module needs to be large enough for the printing process and the scanner to resolve — around 0.4 mm is a common practical minimum for printed material, giving a version 4 code at roughly 16 mm square. Below that, print tolerance and camera resolution start to cause failures, particularly on absorbent materials.
What error correction level should I use?
Level M, around 15%, is a reasonable default for printed material. Level Q or H suits codes that may be dirtied, curved, printed on fabric, or partly covered — including codes with a logo placed over the centre, which relies entirely on error correction to remain readable. Higher levels need more modules for the same data.
Can I put a logo in the middle?
Yes, within limits, and it depends entirely on error correction. A logo covering up to about 30% of a level H code will usually still scan; the same logo on a level L code will not. Always test the final artwork with several devices rather than assuming.
Should I use a shortened URL?
It reduces the data and therefore the module count, giving a physically smaller or more robust code. The trade-off is a dependency on the shortening service continuing to exist, which for printed material with a long life is a real risk. A short URL on your own domain gives both benefits.
Is what I enter stored?
No. Figures are processed in your browser and never transmitted or retained.
Related tools
References
- GOV.UK — product labelling, accessibility and consumer information requirements
- MoneyHelper — guidance on small business marketing costs
Sources are checked at publication and can change — how I choose and check references.