The 10:1 Rule

The simplest way to calculate QR code size is the 10:1 rule: divide the expected scanning distance by 10. If someone will scan from 30cm away (about arm's length), the code should be at least 3cm. From 1 meter, at least 10cm. From 5 meters, at least 50cm. This ensures reliable scanning even in less-than-ideal conditions.

Minimum Size Recommendations

While the 10:1 rule is your guide, here are practical minimums: Business cards: 2cm x 2cm (scanning from ~20cm). Flyers and brochures: 2.5cm x 2.5cm. Product packaging: 2cm x 2cm. Table tents: 3cm x 3cm. Posters (A4/Letter): 4cm x 4cm. Large posters (A2): 6cm x 6cm. Billboards: 30cm+ depending on viewing distance.

Factors That Affect Scanning

Beyond size, several factors affect whether a QR code will scan: Print quality (higher DPI = better scanning). Contrast between code and background. Surface texture (glossy can cause glare). Lighting conditions at the scanning location. Camera quality of typical scanners. Amount of data in the code (more data = denser code = needs more size).

Data Density Matters

QR codes that contain more data have more modules (the small squares), making them denser and requiring larger sizes to scan reliably. A code linking to a short URL might need only 2cm, while one containing a full vCard with photo might need 4cm+. Dynamic QR codes have an advantage here - they always use short URLs.

Print Resolution

QR codes should be printed at sufficient resolution to keep edges crisp. Minimum 300 DPI for close-up scanning, 150 DPI for distance scanning. Blurry edges from low-resolution printing can prevent scanning. Always use vector formats (SVG, PDF) when possible to ensure crisp output at any size.

Common Sizing Mistakes

Making codes too small for the scanning distance. Not accounting for the quiet zone (needs 4 modules of white space around the code). Stretching codes non-proportionally (always maintain 1:1 aspect ratio). Printing at low resolution. Not testing before mass production.