How big does a QR code need to be?

Size calculator

Reading distance in metres

From how far away will it be scanned? A business card about 0.2, a poster 1.5.

Modules per side

Shown in our generator below the preview. 25 is enough for a short link.

Pattern

10.0 cm

with quiet zone

13.2 cm

per module

4.0 mm

What really counts: the individual module

A QR code is made up of square dots called modules. The camera has to be able to make out every single one of them. Whether a code can be read from a given distance therefore depends not on its side length but on how large one module appears in the camera image.

The smallest codes have 21 × 21 modules. Each step up, called a “version” in the standard, adds four modules per side, up to 177 × 177. A short link such as https://qrmacher.de fits into 25 × 25 modules. A link with campaign parameters quickly needs 45, a contact card with every field filled in more than 60. At the same printed size, each module is then correspondingly smaller.

The 1:10 rule of thumb and where it stops

The common rule says: side length equals one tenth of the reading distance. So from two metres, 20 centimetres. That holds for codes with around 25 modules per side. A module is then about one two-hundred-and-fiftieth of the distance, which makes it four millimetres at one metre.

The calculator above uses exactly this ratio, one module per 250th of the distance, and multiplies it by the number of modules. For a short link it gives the same result as the rule of thumb. A dense code with 49 modules, on the other hand, needs almost twice the side length. If you only work with 1:10, you will print it too small.

It is still a rule of thumb, not a standard. New phones with a good camera manage more, older devices in poor light less. An oversized code bothers nobody; an undersized one is worthless. So when in doubt, go bigger.

The quiet zone is part of the space

The code needs a light border four modules wide all round the pattern. That is how the scanner tells where the pattern ends. The calculator therefore gives two measurements: the pattern itself and the area including the quiet zone. For your layout, the second one is what counts, because it is the space nothing else may touch: no text, no edge, no frame.

Our generator sets the quiet zone to four modules automatically and includes it in both PNG and SVG. When you drop the file into your layout, you don’t need to add anything, but you mustn’t crop the border either.

Examples from everyday use

The values are for the pattern without the quiet zone. On the left a short link with 25 modules, on the right a code with 41 modules, such as a link of around 100 characters.

The business card shows why less content is often the better choice. A vCard with two phone numbers, an address and a note quickly reaches more than 60 modules. Read from 20 centimetres, that needs almost five centimetres per side, and on a card measuring 85 × 55 millimetres there is hardly any room left for the name. There is more on this on our page about the vCard QR code.

How many modules does my code have?

Our generator shows the number below the preview, together with the length of the content in bytes. How many modules a code needs depends above all on the length of what it contains. The following overview applies to the default error correction level, M:

Three things push the number up:

• Length of the content. Every character counts. Campaign parameters such as ?utm_source=flyer&utm_medium=print can easily double the length of a link. A tidy address on your own domain is the better choice.
• Umlauts and special characters. The table counts plain characters. An ä, ö or ß takes up two of them, an emoji four.
• Higher error correction. Level Q or H makes the code more robust, but needs room for the extra check data. When that is worth it is explained in the article on error correction.

The lower limit: two centimetres

Even at close range there is a minimum. Phone cameras can only focus so close, and a module of half a millimetre blurs at the edges with any printing process. Below about two centimetres per side, scanning therefore becomes unreliable, even if the calculation for very short distances would come out smaller. The calculator points this out when it happens.

PNG or SVG, and how many pixels?

For print, SVG is the right choice. The file describes the pattern as a vector graphic and stays sharp at any size, from a business card to a construction fence.

If the printer asks for a raster image, resolution matters. The usual figure is 300 dots per inch. A PNG of 2000 pixels per side, the largest size in our generator, is therefore enough for just under 17 centimetres. Anything larger should go to print as SVG. Scaling up a small PNG doesn’t help: the edges of the modules go soft, and those edges are exactly what the scanner relies on.

On screen and on the wall

The same calculation applies to presentations, except that the reading distance is the distance to the back row. From eight metres, a short link needs 80 centimetres on the projection screen. A code tucked small into the corner of a slide simply doesn’t exist for the back rows. Better: a slide of its own with nothing but the code, and the address legible underneath.

Before the print run: once at actual size

The most reliable test costs one sheet of paper. Print the code at the planned size, choosing “Actual size” or “100%” in the print dialog. The default setting “Fit to page” scales the image and skews the test. Then scan it from the planned distance, with an older phone and in the lighting where the code will actually be used.

If that doesn’t work, the article QR code not scanning helps you track down the cause.