What is the minimum size for a printed QR code?

There is no single minimum, because it depends on how much data the code holds and how far away people scan it. For a short URL scanned from hand distance, around 2 to 2.5 cm wide is a common practical minimum. Always print a test and scan it with more than one phone.

How do I convert QR code pixels to cm?

Divide the pixel width by the print resolution in DPI and multiply by 2.54. A 512 px QR code printed at 300 DPI is 512 / 300 x 2.54 = 4.33 cm wide. At 150 DPI the same image prints at 8.67 cm.

How big should a QR code be on a poster?

A commonly used rule of thumb is a code width of about one tenth of the scanning distance. For a poster read from 2 metres, that suggests a code around 20 cm wide. Test at the real distance before printing a full run.

Why does my printed QR code not scan?

The most common causes are a code printed too small, too little white space around it, low contrast or light-on-dark colours, a glossy or curved surface causing glare, and a long URL that makes the pattern dense. Shorten the link, enlarge the code and leave a clear white border.

What Size Should a Printed QR Code Be? cm, Pixels and Distance

The short answer

A printed QR code should be large enough for its modules (the small squares) to be read by a phone camera at the distance people will scan it. For a short link scanned from hand distance, about 2 to 2.5 cm wide is a practical minimum; for a poster, a common rule of thumb is one tenth of the scanning distance. To work out the print size of a PNG, use cm = pixels / DPI x 2.54. The QR Code Generator makes PNGs from 128 to 512 px, which print at about 1.1 to 4.3 cm at 300 DPI.

What decides how small a QR code can be

Three things matter more than the overall size:

How much data it holds. A QR code is a grid of modules. The smallest version is 21 x 21 modules, and each larger version adds 4 modules per side. A long URL needs more modules, so at the same printed size each module is smaller and harder to read. A short link can be printed smaller than a long one.

Scanning distance. A phone needs each module to cover enough pixels on its camera sensor. The further away the code, the larger it must be.

Print quality and contrast. Blurry edges, low-contrast colours, glossy surfaces and curved packaging all reduce the margin for error.

Pixels to centimetres: what the generator's sizes print at

The generator's Size slider goes from 128 to 512 px in steps of 32. The PNG is that many pixels square. Its printed size depends on the resolution your design or print software uses:

PNG size	At 300 DPI	At 150 DPI
128 px	1.08 cm	2.17 cm
256 px	2.17 cm	4.33 cm
384 px	3.25 cm	6.50 cm
512 px	4.33 cm	8.67 cm

The formula is cm = pixels / DPI x 2.54. For inches, skip the 2.54: a 512 px code at 300 DPI is 1.71 inches.

300 DPI is the usual target for sharp print. A QR code is made of large, flat squares, so it tolerates lower resolution better than a photo. Printing the 512 px PNG at 8 to 9 cm (about 150 DPI) normally still scans well. For larger prints, see the poster section below.

Typical sizes by use

These are starting points, not standards. Always test with your actual link and material.

Where it is printed	Typical scan distance	Suggested width
Business card, product label	15 to 25 cm	2 to 2.5 cm
Flyer, menu, table tent	25 to 50 cm	3 to 5 cm
Shop counter sign	50 cm to 1 m	5 to 10 cm
Poster on a wall	1 to 2 m	10 to 20 cm
Banner or window display	3 m or more	30 cm or more

The poster and banner rows follow the one-tenth-of-distance rule of thumb used by many QR and print providers. It is a guide, not part of the QR code standard.

Leave a white border (quiet zone)

Scanners find a QR code by looking for the three large corner squares against an empty background. The QR code specification calls for a clear margin, called the quiet zone, of four modules on every side.

The PNGs from the generator have only a very thin margin, because the QR image service it uses defaults to a 1 pixel margin with no extra quiet zone. So when you place the code in a design:

Put it on a plain light area, not on a photo or pattern.
Leave clear space on all four sides at least four modules wide. Each large corner square is seven modules wide, so the border should be a little more than half the width of a corner square.
Do not let text, lines or the edge of the card touch the code.

Colours and contrast

The generator lets you pick a QR colour and a Background colour. Keep a dark code on a light background with strong contrast: black on white, navy on white, or dark green on pale yellow all work. Avoid:

Light code on a dark background. Many phone cameras read inverted codes, but not all scanner apps do.
Similar shades, such as grey on silver or red on orange.
Metallic or glossy finishes, which reflect light and can wash out parts of the code.

The generator does not offer an error-correction setting, and the image service defaults to the lowest level. That keeps the pattern simple, but it means the code has little tolerance for damage. Do not cover any part of it with a logo or sticker.

Make the code easier to scan at small sizes

Shorten the content. A short URL produces fewer modules, so each one prints bigger at the same size. Remove tracking parameters you do not need.
Use the largest PNG. Generate at 512 px and let your design software scale it down. Scaling down keeps the edges crisp; scaling a small PNG up makes them soft.
Avoid curved surfaces such as bottles and cups for small codes, or make the code larger so the curve does not distort it.
Add a short instruction like "Scan to see the menu". People are more likely to try, and they know what to expect.

Printing a poster-size QR code

A 512 px PNG enlarged to 20 cm or more is printed at under 70 DPI, so the module edges may look slightly fuzzy. Because each module is large at that size, it usually still scans, but check a proof first. If the edges look too soft, ask your printer to scale the image without smoothing ("nearest neighbour" scaling keeps the squares sharp), or recreate the code in software that exports vector files.

Test before you print

Generate the code and download the PNG.

Place it in your design at the intended size, with its white border.

Print one copy on the real paper or material, or at least on plain paper at 100% scale.

Scan it with two or three different phones, from the real distance and under the lighting where it will be used.

Check that the link opens the right page. You can also check the PNG file itself with the QR Code Scanner.

Privacy note

The QR Code Generator creates the image through the free api.qrserver.com service, so the text or link you encode is sent to that service to draw the code. That is fine for public links like a website or review page, but think twice before encoding private information.