QR code size: how big to print for the scan distance

Phone cameras need enough resolved detail in each module (the small squares making up the pattern) to distinguish it from its neighbours at the distance and angle it's being scanned from. Testing across typical phone cameras has converged on a simple, conservative ratio: minimum code width equals scan distance divided by 10.

This is a starting rule, not a hard physical law — a very good camera in bright, even light can sometimes scan smaller, and a scratched lens in low light will need more margin. Treat 10:1 as the size to design for, and always test the actual printed piece before finalising it.

Below roughly 2cm (0.8in) per side, most consumer printers and phone cameras struggle regardless of scan distance — the modules become too fine for typical print resolution and camera autofocus to resolve reliably, even at arm's length. Treat 2cm as a hard floor for anything meant to be scanned by the general public, not just a distance-derived minimum.

This floor matters most on small items: business cards, product labels, name badges. If the item is smaller than 2cm across, consider a lower-density payload (a short dynamic link scans fine at small sizes) or accept that the code needs its own dedicated space rather than being squeezed into a corner.

The quiet zone is the blank margin required around the outside of the pattern — the QR standard specifies at least 4 modules of empty space on all four sides. Scanners use this margin to detect where the code starts and stops; crop or crowd it with text, logos or a border touching the pattern, and scan reliability drops even if the pattern itself is undamaged.

A common mistake is placing a QR code close to a page edge or another graphic element to save space. Leave the full quiet zone as literal empty space (or a plain background), not just a small gap.

Dark modules on a light background scan most reliably. Standard black on white gives maximum contrast, but any high-contrast combination works — dark navy on white, black on light yellow. Avoid similar tones (light grey on white, dark blue on black) and avoid putting the code over a busy photo or gradient background.

If you want a background colour for branding, keep the code itself on a plain white or light card behind it, rather than printing the pattern directly onto a patterned surface.

Printing on a cup, bottle, or curved sign distorts the pattern as the surface wraps away from the camera. Keep codes on the flattest available panel of a curved object, size them larger than the flat-surface minimum to compensate for distortion at the edges, and avoid placing them across a seam or fold.

Textured surfaces (embossed cardboard, fabric, uneven wood) can also break up modules with shadow. Test a physical sample before a full print run on anything other than smooth, flat stock.

Codes displayed on a phone, tablet or monitor for another phone to scan work well because screens are evenly lit and flat, but screen glare and low brightness cause more failed scans than printed paper does. If a code will primarily be scanned from another screen (e.g. a projected slide at an event), oversize it well beyond the 10:1 minimum since screen glare unpredictably reduces effective contrast.