The distance rule
A code scans reliably from about ten times its width. A 2 cm code works from 20 cm, a 10 cm code from a metre, a poster code read from 3 metres needs about 30 cm.
FitMyKB QR
How big to print a QR code
The smallest size that scans depends on distance, how much the code holds and the paper. The rules of thumb that work in print.
Smallest sizes that work
Business cards: 2 cm with a short link. Flyers and menus: 3 to 4 cm. Packaging: 2.5 cm or more. Posters: by distance. Longer content makes denser codes, so shorten links and keep vCards brief.
Quiet zone
Leave a plain margin of at least four modules (the code's small squares) all round. Cropping it is the most common reason a printed code won't scan.
Resolution and format
For print, use SVG or PDF so the code stays sharp at any size; for PNG, 300 DPI at the final size. Never stretch a small image up.
Logos and colours
A logo can cover the middle when error correction is high, but keep it under a fifth of the width. Keep the code darker than the background; inverted (light on dark) codes fail on some phones.