What size should a printed QR code be?

The most common rule: the code should be at least one tenth as wide as the distance it is scanned from. A code read from 1 metre should be at least 10 cm wide. The calculator does the maths for you.

Distance the code will be scanned from, in metres

Minimum code size: 10 cm that is 1,181 px at 300 dpi

Add 10 to 20% for a dotted, heart, round or logo code.

Size table

Material	Scanning distance	Minimum size
Business card	20 to 30 cm	2 to 3 cm
Flyer, menu, table stand	30 to 50 cm	3 to 5 cm
A3 poster	1 m	10 cm
Shop window	1.5 to 2 m	15 to 20 cm
Vehicle, sign	3 to 5 m	30 to 50 cm

What forces a bigger code

Long content: a 120-character address gives far more small squares than a short one. An editable code stays compact because it only holds a short link.
A logo in the centre: it requires higher error correction, so a denser code.
Custom shapes (dots, heart, round): allow 10 to 20% more.

Mistakes to avoid

Cropping the light margin around the code (at least 4 small squares): without it, many phones fail.
Printing light on dark, or in pale grey: keep a dark code on a light background.
Enlarging a small PNG: use the SVG for large formats, it stays sharp at any size.
Sticking the code on a strongly curved surface (small bottle, narrow pole).

In pixels, for your printer

At 300 dots per inch, standard print quality, a 3 cm code is about 354 pixels and a 10 cm code about 1,181 pixels. The QR Durable PNG is 2,000 pixels: enough up to about 17 cm. Beyond that, send the SVG.

Questions

What is the absolute minimum size?

In practice 2 cm wide, for a short code read up close. Below that, many phones struggle to focus.

Is a code too big a problem?

No, as long as it fits entirely in the camera frame at the planned distance.