QR Code Size Guide

Why size matters: the physics of scanning

A smartphone camera scanning a QR code needs to resolve each individual module — the small black and white squares that make up the code. The camera's resolution, the ambient lighting, and the distance between the phone and the code all interact. If the modules are too small relative to the scanning distance, the camera cannot distinguish them, and the scan fails.

The ISO/IEC 18004 standard defines a QR code's size in terms of modules, not physical dimensions. A version 1 QR code is 21×21 modules. A version 40 QR code is 177×177 modules. As you encode more data, the version number increases, and the code becomes denser and requires a larger physical size to remain scannable.

This is why two QR codes of the same physical size can have very different scan reliability: one encoding a short URL and one encoding a vCard with a long address store very different amounts of data. More data means more modules means smaller modules at the same physical size.

Minimum sizes for common applications

These are the minimum sizes for reliable scanning in typical conditions. Always aim larger when possible.

Business cards (85×55 mm): minimum 1.5 cm × 1.5 cm QR code, though 2 cm × 2 cm is more reliable. At 1.5 cm, the code needs to encode short content — a URL under 50 characters, not a full vCard.

Table cards and tent cards: minimum 2.5 cm × 2.5 cm. This size works from 20–30 cm scanning distance, typical for someone sitting at a table.

A4 and A5 posters: minimum 3–4 cm × 3–4 cm. At this size the code can encode a longer URL and remains scannable from 30–50 cm.

A3 and A2 posters: minimum 5–6 cm × 5–6 cm, scaling up if people will scan from further away. A common rule of thumb is that scanning distance is about ten times the code width, so a 5–6 cm code suits roughly 50–60 cm.

Billboards and large format: the rule is 10 cm per metre of typical viewing distance. A billboard viewed from 5 metres needs a QR code at least 50 cm × 50 cm.

Product packaging: varies by product. On a small label, 2 cm × 2 cm minimum. On a box or bag, 3–4 cm × 3–4 cm to allow for handling and variable distances.

The quiet zone: the margin you cannot skip

Every QR code specification requires a quiet zone — a clear border of white space around all four sides of the code. The standard defines this as at least four modules wide (matching the module size of the code itself).

For practical purposes, add at least 4 mm of clear white space around the entire code at normal print sizes. Without the quiet zone, scanners have difficulty identifying where the code begins and ends, and scan failure rates increase significantly.

A common mistake is placing a QR code flush against a design element, image, or the edge of a label. The visual result might look clean, but the functional result is reduced scan reliability. Always maintain the quiet zone.

Colour and contrast: the second most important factor

After size, contrast is the factor that most affects scan reliability. A QR code's dark modules need to be clearly distinguishable from its light background by the camera.

Black modules on a white background: maximum contrast, maximum reliability. This combination is always the first choice when no branding constraint prevents it.

Dark brand colour on white: generally fine. Dark navy, dark green, dark brown on white all work well. The key is keeping the module colour dark enough.

Light modules on dark background: this reversal (called inverted QR code) works on many modern devices but has lower reliability on older devices. If you use this approach, test on multiple devices including older smartphones.

Gradient backgrounds: avoid placing a QR code on a gradient that transitions through medium-contrast zones. The scanner evaluates the entire code area, and inconsistent contrast causes read errors.

Printed on coloured paper or card: saturated red and orange papers reduce luminance contrast against dark modules, and mid-tone papers do the same. Dark modules on a mid-tone coloured card are problematic. Black on white, black on light grey, or dark navy on cream all work reliably.

Download format and print resolution

Size and format interact at print time. A QR code image downloaded at 200×200 pixels and then printed at 10 cm × 10 cm will appear at roughly 50 DPI — visibly blurry, with degraded scan performance.

For reliable print quality, the rule is a minimum of 300 DPI at the intended print size. At 300 DPI: - 3 cm × 3 cm print requires at least 354 × 354 pixels - 5 cm × 5 cm print requires at least 591 × 591 pixels - 10 cm × 10 cm print requires at least 1181 × 1181 pixels

The practical solution is to always use SVG format for print. SVG is a vector format that is mathematically defined and renders at any size without loss. An SVG file is equally sharp at 3 cm or 3 metres. This completely eliminates print resolution as a concern.

Testing at the actual intended size

After choosing your size and format, print a test copy at the exact intended size and test it before committing to a large print run.

Test with the phone in the actual position users will be in. For a table card, hold the phone at arm's length as someone might while reading a menu. For a wall poster, stand at the distance where a typical viewer would notice it and decide to scan.

Test in the actual lighting conditions. A QR code on a restaurant table that looks fine under overhead lighting may fail to scan in the candlelit corner tables. A code on a window decal that works in shade may reflect too much sunlight to scan during afternoon hours.

Test with multiple devices. An iPhone 15 has a better camera and image processing than a 2018 Android mid-range device. If your audience is likely to include people with older phones, test on an older phone.