Most QR code failures come down to size, not the generator. Here's a practical reference covering print sizes, error correction levels, and data capacity — the three variables that determine whether a QR code works reliably in production.
Print Size Reference
The rule: for every 1 metre of scan distance, your QR code should be at least 10 cm × 10 cm.
| Use Case | Recommended | Minimum | Scan Distance |
|---|---|---|---|
| Business card | 2 × 2 cm | 1.5 × 1.5 cm | 10–20 cm |
| Flyer / brochure | 3–4 × 3–4 cm | 2 × 2 cm | 20–40 cm |
| Poster (A3) | 6–8 × 6–8 cm | 4 × 4 cm | 60–100 cm |
| Banner / signage | 10+ cm | 8 × 8 cm | 100–200 cm |
| Restaurant tent card | 4 × 4 cm | 2.5 × 2.5 cm | 25–50 cm |
| Email signature | 80–120 px | 80 × 80 px | Screen |
| Digital display | 150 × 150 px | 100 × 100 px | 30–60 cm |
Error Correction Levels
| Level | Damage Tolerance | Use Case | Density |
|---|---|---|---|
| L | 7% | Screens, clean indoor print | Lowest |
| M | 15% | General — most printed materials | Low |
| Q | 25% | Outdoor, expected wear | Medium |
| H | 30% | Logo overlays, outdoor signage | Highest |
Practical guide: Use Level M for everything. Use Level H only when adding a logo over the QR code — the logo covers the centre, so you need the extra redundancy.
Data Capacity
| Content | Max Characters | Practical Target |
|---|---|---|
| URL | ~2,953 | Under 100 chars |
| Plain text | ~2,953 bytes | Under 500 chars |
| WiFi string | — | ~100–150 chars |
| vCard | — | ~200–500 chars |
Shorter input = less dense code = better scanning.
Common Mistakes
1. Downloading at 256 px, printing large
A 256 px image at 10 cm × 10 cm prints at ~65 DPI. Use 1024 px for anything printed larger than 4 × 4 cm.
2. Logo without Level H correction
Without H correction, covering the centre of a QR code causes scan failures. Always set Level H before generating a code you'll overlay with a logo.
3. Cropping the quiet zone
The white border around the code (quiet zone) must be at least 4 modules wide. Scanners use it to detect the code boundary. Cropping it makes codes unreliable even if they look intact.
Testing Checklist
Before printing any quantity, test with:
- iPhone native Camera app
- Google Lens or Android native camera
- A dedicated scanner app (QR & Barcode Scanner)
Scan from your screen first, then from a printed test copy at the intended scan distance.
For one-off generation: a free QR code generator handles URL, text, WiFi, and vCard, downloads at 256/512/1024 px, and generates static codes with no expiration — nothing uploaded to any server.
Originally published at https://snappytools.app/qr-code-generator/