The most common reason a QR code doesn't scan isn't the design — it's the size. Print one too small and even the best scanner in the world will struggle. Here's the actual rule, plus practical numbers for the formats you're most likely to print.
The one rule that matters
The size of your QR code should be roughly 1/10th of the distance from which someone will scan it.
That's it. Memorize that ratio and most sizing decisions become trivial.
- Scan from 1 foot (30 cm)? QR should be about 1.2 inches (3 cm).
- Scan from 6 feet (2 meters)? QR should be about 8 inches (20 cm).
- Scan from 20 feet (6 meters) — a billboard? QR should be about 24 inches (60 cm).
This isn't a marketing rule of thumb — it's the practical limit of phone camera autofocus combined with the minimum module size scanners can resolve.
Practical sizes by use case
| Use case | Typical scan distance | Recommended QR size |
|---|---|---|
| Business card | 4–8 inches (10–20 cm) | 0.8–1 inch (2–2.5 cm) |
| Flyer or postcard | 8–12 inches (20–30 cm) | 1–1.5 inches (2.5–4 cm) |
| Restaurant menu (table) | 12–18 inches (30–45 cm) | 1.5–2 inches (4–5 cm) |
| Storefront window | 3–6 feet (1–2 m) | 4–8 inches (10–20 cm) |
| Trade show booth banner | 6–10 feet (2–3 m) | 8–14 inches (20–35 cm) |
| Yard sign | 6–15 feet (2–4.5 m) | 8–20 inches (20–50 cm) |
| Billboard | 50+ feet (15+ m) | 5+ feet (1.5+ m) |
Round up if you're unsure — slightly oversized never hurts, undersized fails.
The minimum-size floor
Even for very close scanning, don't go below 0.8 inches (2 cm) on print. Phone cameras can technically resolve smaller, but you give up margin for:
- Customers holding their phone at odd angles
- Slightly blurry prints
- Glare on glossy paper
- Older phones with worse cameras
For QR codes with a logo in the middle, bump that minimum to 1 inch (2.5 cm). The logo subtracts from the data area, so the surrounding modules need more space to compensate.
Resolution and file format
This trips people up: size in inches and resolution in pixels are different things.
For digital screens (emails, websites): a PNG at the actual display size works. ~300×300 pixels is plenty for most uses.
For printing: use the SVG if you have it. SVG is vector — it scales infinitely without losing quality. If you only have a PNG, make sure you have a high-resolution version. Rule of thumb: pixels = inches × 300 DPI. For a 2-inch printed QR you want at least 600×600 pixels. Less than that and you'll see jagged edges in print.
OneDollarQRcodes gives you both PNG and SVG with every download for exactly this reason.
The quiet zone (don't skip this)
Every QR code needs a "quiet zone" — a blank margin around the code with no other graphics or text. The minimum is 4 modules wide on every side (where a "module" is one pixel of the QR's grid). Visually, that's about the width of one of the corner squares.
Skip the quiet zone and scanners can fail to find the code at all, especially against busy backgrounds. If your QR is sitting on a photo or a colorful pattern, pad it with a solid white square first.
Contrast: black on white wins
Black on white scans best. Every other color combination scans worse.
That doesn't mean don't use color — branded QR codes work fine — but you have to maintain at least a 4:1 contrast ratio between the QR and its background. Use any contrast checker (WebAIM is the standard) to verify. A dark navy or deep maroon QR on white background reads almost as well as black; a medium gray QR does not.
Invert at your peril: white-on-black usually works on smartphones but trips up older scanners and some Android variants. If you must do it, test extra carefully.
When in doubt, print one
The single best test: print one at your final intended size, on the final paper stock, then scan it from the actual distance your customer will. Do this with both an iPhone and an Android phone. If both work, you're safe to commit to the print run.