Optimal QR Code Size - A Design Guide by Scanning Distance
Basic Sizing Principles
QR code size must scale with scanning distance. The general rule is to make the code at least one-tenth of the scanning distance. For 30cm, you need at least 3cm; for 1m, at least 10cm.
These are minimums. Actual requirements vary with QR code version, print quality, and lighting. Adding a 1.5x safety margin to the calculated size is recommended.
Recommended Sizes by Medium
Recommended sizes for common media:
| Medium | Distance | Size | Notes |
|---|---|---|---|
| Business card | 15-20cm | 2cm+ | Keep data minimal |
| A4 flyer | 20-30cm | 3cm+ | Ensure adequate margins |
| A3 poster | 50cm-1m | 5-10cm | Consider lighting |
| Outdoor sign | 1-3m | 15-30cm | Use error correction H |
| Large banner | 3-5m | 30-50cm | High-res printing required |
These are guidelines. Always test scan in the actual environment.
Calculating Module Size
Scan reliability depends not just on overall size but on individual module (smallest black/white unit) size. Smartphones need modules of at least 0.5mm for reliable scanning.
Module size equals QR code side length divided by module count. A Version 3 code (29x29 modules) printed at 3cm gives modules of about 1.03mm, which is adequate.
Higher versions have more modules, so the same print size yields smaller modules. Reducing data to fit a lower version is key to maintaining scan reliability.
Printing Considerations
Key points for printing QR codes:
- Resolution: Print at 300dpi minimum. Low resolution blurs module boundaries.
- Quiet zone: Maintain at least 4 modules of white space around the code.
- Paper finish: Glossy paper can cause glare. Use matte for indoor displays.
- No scaling: Photocopying at reduced size can make modules too small to scan.
Related: See also our guide on QR code print guide.
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The Importance of Test Scanning
Even correctly sized codes may fail in real conditions. Always test:
- Scan from the maximum expected distance
- Test on multiple devices (both iOS and Android)
- Test under actual lighting (fluorescent, natural, dim)
- Test scanning at an angle
If issues arise, increase size, raise error correction level, or reduce data. Investing time in pre-print testing prevents costly reprints.