Why Size Matters
A QR code that is too small to scan is worse than no QR code — it wastes print real estate and frustrates users who try and fail. Understanding the relationship between physical size, QR version, and scanner capability lets you specify the correct minimum size for every application.
The Fundamental Relationship
A QR code is made up of modules (the small squares). The minimum physical size is determined by:
modules × minimum module size.
The minimum module size a camera can reliably resolve is approximately 0.25 mm under ideal conditions (good lighting, close range, modern phone). For reliable performance across all conditions, use a minimum of 0.5 mm per module.
| QR Version | Module Count | At 0.5mm/module | At 1mm/module |
|---|---|---|---|
| V1 | 21 × 21 | 10.5 × 10.5 mm | 21 × 21 mm |
| V3 | 29 × 29 | 14.5 × 14.5 mm | 29 × 29 mm |
| V5 | 37 × 37 | 18.5 × 18.5 mm | 37 × 37 mm |
| V10 | 57 × 57 | 28.5 × 28.5 mm | 57 × 57 mm |
For typical business card and label applications (V2–V5), the practical minimum is 25 × 25 mm for reliable scanning under normal conditions.
ISO/IEC 18004 Minimum Size Guidance
The QR code standard does not specify a hard minimum size — it specifies a minimum module size relative to the reader system's capabilities. For consumer smartphone scanning, the practical industry minimum is:
- 25 × 25 mm for typical content (URL, vCard, WiFi credentials)
- 20 × 20 mm only for very simple content (V1–V2) with Level H error correction under ideal conditions
Minimum Sizes by Use Case
| Application | Recommended Minimum | Notes |
|---|---|---|
| Business card | 20 × 20 mm | V1–V3 only; test before printing |
| Product label | 25 × 25 mm | Standard reliable minimum |
| A5/A4 flyer | 30 × 30 mm | Slightly larger for low-quality print |
| Outdoor poster (< 2m) | 40 × 40 mm | For 1m scanning distance |
| Outdoor billboard (> 2m) | Use sizing formula | See distance section |
Effect of Error Correction Level
Higher error correction levels (Q, H) add more data to the QR, increasing the version number and module count. This means a V5 QR at Level H is larger than a V3 QR at Level L for the same content. For size-constrained applications, use Level M or L and compensate by optimising your content (use short URLs, avoid unnecessary data).
The Quiet Zone
Every minimum size specification assumes the quiet zone (4-module white border) is included. A QR printed at 25 mm with the quiet zone not factored in is effectively smaller and may fail to scan. Always add the quiet zone to your size specification.
Related tools and guides
- Use the [QR size calculator](/qr-size-calculator) to match the printed size to the expected scan distance before you commit to a print run.
- Check print proofs with the [printed QR tester](/printed-qr-tester) so problems show up before a full run.
- The [QR size guide](/qr-size-guide) gives size recommendations for common placements.
- Test every code with the [QR scanner](/qr-scanner) on more than one phone before you publish or print it.
- The [scan guide](/scan-guide) explains how phone cameras find and decode a code.
- The [QR placement guide](/qr-placement-guide) covers height, lighting, glare, and surfaces that affect scan success.
