The Distance Rule for Outdoor QR Codes
A QR code must be large enough to be captured clearly by a smartphone camera at the intended scanning distance. The formula:
QR size (mm) = Scanning distance (metres) × 10
| Scanning Distance | Recommended Minimum QR Size |
|---|---|
| 0.3 m (arm's length) | 30 × 30 mm |
| 0.5 m (typical standing) | 50 × 50 mm |
| 1 m (at a poster) | 100 × 100 mm |
| 2 m (shop window) | 200 × 200 mm |
| 3 m (A-frame / kerb sign) | 300 × 300 mm |
| 5 m (large banner) | 500 × 500 mm |
| 10 m+ (billboard) | QR codes not practical |
At distances above 5–6 metres, the scanning experience degrades significantly — smartphone cameras struggle to resolve and focus a QR at this range in real-world conditions. Billboards at 10+ metres should not rely on QR codes as the primary response mechanism.
A-Frame and Pavement Sign
An A-frame sign viewed from the pavement requires a QR of at least 150 × 150 mm for comfortable scanning from a standing position at 1.5m. Place the QR at the top third of the sign where it is closest to eye level when the viewer has stopped to read the sign.
Shop Window QR
Scanning from outside a shop window (1.5–2m): minimum 150–200 mm QR. Factors that reduce effective scan distance:
- Glass reflections (mitigated by scanning at angle)
- Frosted or tinted glass (avoid placing QR behind these)
- QR on the interior side of the glass (double the glass reflection risk)
Best practice for shop windows: Print the QR on a vinyl sticker applied to the outside surface of the window. This eliminates glass reflection and maximises contrast.
Environment and Lighting Considerations
Bright direct sunlight: Gloss materials cause glare. Use matte vinyl or add anti-glare laminate.
Artificial interior lighting: QR codes in shop windows or on illuminated signage face changing light conditions through the day. Test scanning at peak contrast reduction times (noon sunlight for west-facing windows).
Night and low light: Standard QR codes are passive — they do not emit light. In low-light environments, the scanning area must be illuminated. A small light directed at the QR (common in hospitality settings) dramatically improves night scanning.
Putting this into practice
Start with the smallest real test you can run. Generate the code, print it at the exact size you plan to use, and scan it with two different phones in the lighting where it will live. Check that the destination page loads quickly on a mobile connection and that the call to action next to the code tells people what they will get. If anything feels slow or unclear, fix it before you print a full batch, because reprints cost more than a short test. Keep a note of the size, material, and placement that worked so the next batch starts from a proven setup.
Common mistakes to avoid
The most common mistakes are easy to avoid once you know them. Long payloads make modules tiny, low contrast makes edges hard to read, and text placed too close to the border eats the quiet zone the scanner needs. Covering a corner finder pattern with a logo or a sticker breaks detection entirely, and a code placed behind glare or on a curved surface fails even when the print is perfect. Review each of these points on a proof copy, and treat any failure as a reason to adjust the design rather than a reason to blame the scanner.
Quick checklist
- Keep the payload as short as practical so modules stay large.
- Keep dark modules on a light background with strong contrast.
- Leave a clear quiet zone on all four sides of the symbol.
- Test the printed code at the real viewing distance and lighting.
- Confirm the destination page loads fast on a phone.
- Recheck the code after any change to the link, design, or placement.
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.
- The [QR placement guide](/qr-placement-guide) covers height, lighting, glare, and surfaces that affect scan success.
- Test every code with the [QR scanner](/qr-scanner) on more than one phone before you publish or print it.
- When a one-dimensional symbol fits better, the [barcode generator](/barcode-generator) covers retail and inventory formats.
