The rule of thumb: distance divided by 10
A QR code is reliably readable from about ten times its width. A 3 cm code works from about 30 cm, a 10 cm code from about 1 m. Turned around: divide the expected scanning distance by 10 to get the minimum width.
This is a guideline, not a law. Good light, a modern phone and a short link allow a little more, a dense code and a dim room require a little less.
Size table for common uses
| Use | Typical distance | Recommended width |
|---|---|---|
| Business card | 15 to 25 cm | 2 to 2.5 cm |
| Flyer, invitation | 20 to 30 cm | 2.5 to 3 cm |
| Table stand, menu | 30 to 50 cm | 3 to 5 cm |
| Packaging, label | 20 to 40 cm | 2 to 4 cm |
| Poster at eye level | 1 to 2 m | 10 to 20 cm |
| Shop window | 1 to 3 m | 10 to 30 cm |
| Banner, trade fair wall | 5 to 10 m | 50 to 100 cm |
Never go below 2 × 2 cm, even when people scan from very close. Many phones cannot focus closer than about 10 cm.
Why the content affects the size
The more characters a code contains, the more modules (the small squares) it has. A short link needs a grid of about 25 × 25 modules, a long contact card can easily need 50 × 50 or more. At the same print size every module gets smaller, and the phone has to come closer.
Keep the content short: a short link instead of a long tracking address, and only the necessary fields on a business card QR code. A logo also makes the code a little denser, because Scanoli then uses the highest error correction.
Do not forget the quiet zone
Around the code there must be a light margin, called the quiet zone. The QR code standard recommends four modules. Scanoli adds this margin by default (Advanced, Margin). Text, lines or images placed too close to the code make it harder for scanners to find its edges.
The right resolution for print
For print, vector formats are best: SVG and PDF stay sharp at any size, and print shops can use them directly. If you need a raster image such as PNG, calculate with 300 dpi: width in cm divided by 2.54, multiplied by 300, gives the pixels.
| Print width | Pixels at 300 dpi |
|---|---|
| 2.5 cm | about 300 px |
| 5 cm | about 600 px |
| 10 cm | about 1,200 px |
| 20 cm | about 2,400 px |
| 40 cm | about 4,700 px, better SVG or PDF |
In Scanoli you can export PNG, JPG and WebP up to 4096 px, and SVG and PDF without any size limit.
Checklist before printing
- Calculate the size: distance divided by 10, at least 2 cm.
- Keep the content short and test the link.
- Use SVG or PDF, or PNG with at least 300 dpi.
- Keep the quiet zone free.
- Print a test page at the real size and scan it from the planned distance with two or three phones.
