The most common reason a QR code fails to scan is not the content or the generator — it's the size. Too small, and scanners can't resolve the pattern. Too large, and you waste space. Here's a practical reference for every common use case.
QR Code Print Size Reference
| Use Case | Recommended Size | Minimum Size | 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/A2) | 6–8 × 6–8 cm | 4 × 4 cm | 60–100 cm |
| Banner / signage | 10+ × 10+ cm | 8 × 8 cm | 100–200 cm |
| Restaurant table tent | 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 |
| T-shirt / merchandise | 5 × 5 cm | 3 × 3 cm | 20–50 cm |
The general rule: for every 1 metre of intended scan distance, your QR code should be at least 10 cm × 10 cm.
Error Correction Levels
Error correction determines how much of the QR code can be damaged or obscured while still scanning reliably.
| Level | Damage Tolerance | Best For | Code Density |
|---|---|---|---|
| L (Low) | 7% | Digital screens, clean print | Lowest |
| M (Medium) | 15% | General use, most printing | Low |
| Q (Quartile) | 25% | Outdoor print, some wear | Medium |
| H (High) | 30% | Logo overlays, outdoor signage | Highest |
Rule of thumb: Use Level M for most purposes. Use Level H if you're overlaying a logo on the QR code (the logo covers the centre — you need extra redundancy to compensate).
The Quiet Zone
One thing most guides skip: the quiet zone — the white border around the QR code. It must be at least 4 modules wide (4× the size of one small square in the pattern). Never crop this border. Scanners use the quiet zone to detect where the code starts and ends; without it, scanning becomes unreliable.
Data Capacity by Content Type
| Data Type | Max Characters | Practical Limit |
|---|---|---|
| Numeric only | 7,089 | ~3,000 |
| Alphanumeric | 4,296 | ~2,000 |
| Binary / text | 2,953 bytes | ~500–1,000 chars |
| URL (short) | — | 50–100 chars ideal |
| WiFi QR string | — | ~100–150 chars typical |
| vCard | — | ~200–500 chars typical |
Shorter = simpler = more reliable. A QR code containing https://example.com is much less dense than one containing a 400-character vCard. Use a URL shortener if your URL is long.
Testing Before Printing
Always test before printing. Use at least two different devices:
- iPhone native Camera app
- Google Lens (Android) or Android native camera
- A dedicated QR scanner app as a backup
Test at the intended scan distance. A business card QR code that scans fine at 5 cm on your screen may fail at 20 cm on a printed card.
Common Mistakes
Mistake 1: Generating at preview resolution, printing at actual size
If you download a 256 px QR code and print it at 10 cm × 10 cm, the DPI is only about 65. For sharp print, use the highest resolution download (1024 px) and print at the appropriate physical size.
Mistake 2: Adding a logo without using Level H error correction
Logos cover the centre of the QR code. At Level L or M, even 10% coverage causes scan failures. Set error correction to Level H before generating a code you plan to overlay with a logo.
Mistake 3: Dark background with light modules
Most scanners expect dark modules on a light background. Inverted QR codes (light on dark) fail on older apps and some cheap QR scanners. Stick to dark-on-light unless you test thoroughly.
Generate One Now
A free QR code generator handles URL, text, WiFi, and vCard inputs, lets you download at 256 px, 512 px, or 1024 px, and generates static codes with no expiration — no account, no watermark, nothing uploaded to a server. Your input stays in your browser.
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