How big should a printed QR code be?

Two things decide the size

A phone camera has to see each small square of the code, called a module, clearly. So the printed size depends on two things:

• How far away people will scan from. A business card is scanned from 15 cm, a poster from a metre or more.
• How many modules the code has. That grows with the amount of text you put in it.

A widely used rule of thumb is that the code should be at least one tenth of the scanning distance wide: about 2 cm for a card held in the hand, 10 cm for a poster read from a metre away, 30 cm for a sign across a room. Give yourself more margin for low light, glossy paper or curved surfaces like cups.

Shorter links make easier codes

We generated codes with the same library QR Code Generator uses, at its default error correction level (M):

• https://www.deskumo.com (23 characters): 25 × 25 modules.
• A 103-character campaign link with tracking parameters: 41 × 41 modules.
• The same long link at the highest error correction (H): 57 × 57 modules.

The code is also surrounded by a blank margin, the *quiet zone*, which the tool sets to 4 modules on each side by default. Print the code at the same physical size and the long link’s modules are much smaller, which makes it harder to scan. If you can, shorten the link or drop tracking parameters you don’t need.

Module size at common print sizes

Here is how big each module ends up, including the 4-module quiet zone in the printed size:

• 2 cm wide: 0.61 mm modules for the short link, 0.41 mm for the long one.
• 3 cm wide: 0.91 mm and 0.61 mm.
• 5 cm wide: 1.52 mm and 1.02 mm.

As a practical floor, keep modules at roughly half a millimetre or more for anything people will scan by hand. That means a short link works at 2 cm, while the long one is better at 3 cm or more. These figures are calculated, not a lab test, so for a large print run always test a proof with a couple of different phones.

Settings for printing

• Download SVG for print. SVG is a vector format, so it stays sharp at any size and print shops prefer it. Use PNG for screens, documents and messages; at 1,024 px a PNG is enough for a code up to about 8 cm at 300 DPI.
• Keep the quiet zone. Don’t crop the white border, and don’t place the code on a busy background without it.
• Contrast matters more than colour. Dark code on a light background scans best. Light codes on dark backgrounds aren’t read by every scanner app.
• Raise the error correction level (Q or H) only if the code may be scuffed, partly covered or printed on a rough surface. It makes the code denser, so increase the size to match.

Before you print 500 copies

Print one copy at the real size. Scan it with at least two phones, an iPhone and an Android if you can, from the distance people will actually stand. Check that the link opens the right page and still works on mobile data, not just your office Wi-Fi.

Codes made with deskumo contain the link directly, with no redirect service in between, so they never expire: they work for as long as the page they point to exists.

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