QR Code Size and Resolution Guide

QR Code Size and Resolution

A QR code that's too small won't scan reliably; one that's too large wastes space. The optimal size depends on scanning distance, content length, and the print or display medium.

Minimum Size Formula

The general rule is that a QR code should be at least 1/10th of the expected scanning distance. For a poster viewed from 1 meter, the QR code should be at least 10cm. For a business card scanned from 15cm, 1.5cm minimum. This assumes good lighting and a modern smartphone camera.

Module Size Matters

Each small square in a QR code is called a module. For reliable scanning, each module should be at least 0.75mm in print (about 3 pixels at 100 DPI). As the data content increases, the QR code contains more modules in the same physical space, making each module smaller. A QR code encoding a 20-character URL might have 25×25 modules, while a 300-character text block requires 57×57 modules.

Print vs Screen

For print, generate at minimum 300 DPI. Newspaper and offset printing can introduce dot gain that fills in small modules — increase the minimum module size to 1mm for these media. For screen display, ensure each module is at least 4×4 CSS pixels. On retina displays, the physical pixel count is doubled, so the visual appearance is fine even at 2×2 CSS pixels.

Testing Protocol

Always test printed QR codes with at least three different smartphone models under realistic lighting conditions. Test at both the expected and maximum scanning distances. If more than 10% of test scans fail, increase the physical size or reduce the encoded data length.