Sheet 05 · the craft
Printed too small, every code fails.
Size, contrast, quiet zone, surface. Four variables, and almost every failed scan is one of them. Here are the numbers that actually work in print.
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The only sizing table you need
Every failed QR code I have ever seen failed for one of four reasons: too small, too little contrast, no quiet zone, or a surface that could not be scanned flat. Size is the first variable, and it is the easiest to get wrong.
| Use | Scanning distance | Minimum print size | Module size |
|---|---|---|---|
| Business card | 10–15 cm | 18 mm | 0.5 mm |
| Flyer, table card | 20–30 cm | 25 mm | 0.6 mm |
| Poster, A3 | 1 m | 60 mm | 1.2 mm |
| Shop window, A2 | 2–3 m | 120 mm | 2 mm |
| Billboard | 10 m and beyond | 600 mm | 1 cm |
A rough rule that scales better than any table: the code's width should be at least one tenth of the scanning distance.
The four failure modes
Too small. The phone cannot resolve individual modules. This is the one people blame on the generator.
Too low contrast. Grey on white, or a brand colour with a similar brightness to the background. Measure it: if the two colours look the same in a black and white photo, they will fail.
No quiet zone. Cropping the blank margin to let a logo sit closer is a reliable way to break a code that tested fine on screen.
Bad surface. Glossy paper, curved bottles, glass with a reflection behind it. Matte, flat and evenly lit.
Error correction, in one paragraph
A QR code can survive damage because it carries redundant data. Level L tolerates about 7% of the code being unreadable, M about 15%, Q about 25%, and H about 30%. Higher levels hold fewer characters in the same square, which makes the pattern denser and the modules smaller. So there is a real trade-off: H helps a scuffed laminate, but hurts a print that was already too small. Pick M and print bigger before reaching for H.
Sizing questions
What is the smallest a QR code can be printed?
About 2 cm for close scanning with a modern phone, 3 cm for arm's length on a poster, and 10 cm or more for something read from several metres like a billboard.
What is a quiet zone?
The blank margin around the pattern. The specification asks for four modules. Without it scanners struggle to find the edges of the code.
Does colour hurt scannability?
Contrast does. Dark ink on light paper always works. Light on dark fails on many scanners. Two mid-tone colours with similar brightness fail on almost all of them.
What resolution does a PNG need?
At least 4 pixels per module, and 8 or more for screens at 2x density or print. This generator goes up to 20.
Which error correction level should I use?
M for most things, Q or H for small prints, curved surfaces, or anything likely to get scuffed.
Other sheets
QR Forge Desktop — $19 once
Everything on this page, minus the browser tab and the limits: batch generation from a CSV, your logo in the middle, vector PDF for print shops, and a folder you can keep on a machine that never goes online.