What is the Right Size for Printing a QR Code? Recommended and Minimum Sizes Explained

Introduction: Considering the Minimum and Recommended Size of a QR Code

QR codes are an indispensable tool for modern information sharing.

They are used on a variety of printed materials, from business cards, brochures, flyers, and leaflets to large signboards. However, choosing the wrong size for a QR code can make it difficult to read or visually unappealing.

Therefore, it is important to select the appropriate size for each usage scenario.

For example, when used in a small space like a business card, the QR code may be too small to be scanned easily.

On the other hand, in situations where it is viewed from a distance, like on a signboard, it may not be readable if the size and contrast are not appropriate.

This article explains the minimum and recommended sizes for QR codes for different scenarios and introduces key points to be aware of during creation and printing.

The Minimum Size of a QR Code

When printing a QR code at its minimum size, the most important factor is that it must be readable. Here, we will explain the minimum size for both printed materials and digital environments.

Minimum Size for Printed Materials

When using a QR code on printed materials, the following formula is generally a good reference: "1 cell (black or white square) of a QR code = 0.4mm or more"

Assuming a printer's supported density is 350 dpi and one cell is printed with 5 dots, the calculation results in approximately 0.36mm per cell, which we will round up to 0.4mm.

Here, let's consider creating a QR code for this URL (https://qr-stock.com) with an error correction level of M.

What is an error correction level?

The QR code was created with QR STOCK.

For this URL with error correction level M, the version was 2.

A version 2 QR code has a structure of 25x25 cells. In this case, if one cell is 0.4mm, a QR code of at least 11.6mm square is required. Adding a margin equivalent to 4 cells = 1.6mm, theoretically, a QR code of at least 13.2mm square is necessary.

Minimum Size for Web Use, such as Social Media

When posting a QR code on social media or a website, it is not necessary to be as strict about the cell size as with printed materials. However, a minimum image size of 150px × 150px is recommended. This is a standard that allows for smooth reading by most smartphone cameras.

In the Case of Retina Displays

A Retina display is a high-resolution display featured in Apple products (iPhone, iPad, MacBook). If you use an image at its original size on a Retina display, it may appear blurry. To display it clearly, you need to double the image resolution. For example, if the standard is 150px × 150px, 300px × 300px or more is desirable for Retina support. If you save the QR code in SVG format, you can use it without worrying about resolution.

Procedure for Confirming the Minimum Size of a QR Code

You can determine the minimum size of a QR code by following these steps.

STEP1. Confirm the Number of Cells from the QR Code's Version

To find the minimum size of a QR code, you need to know the number of cells, which is not something a person can determine at a glance. The number of cells increases as the data capacity increases. To check the number of cells, you need to confirm the "version" of the created QR code. Most QR code creation services (including QR STOCK) set the version automatically.

For a short URL, it might be version 1 or 2, but for a long URL or a large amount of text, it could be version 10 or higher.

Let's use the free online QR code creation and reading tool, QR STOCK, to check the version.

1-1: Check the version of the created QR code

Access the following URL and check the version of your created QR code. How to Check a QR Code's Version

1-2: Check the number of cells for that version The number of cells in a QR code is determined by its version. Check the number of cells from the version list in the article below.

QR Code Version and Cell Count List

The number of cells for version 2 is 25.

STEP2. Confirm the DPI Recommended by the Printing Service

When using QR codes on printed materials, the DPI (dots per inch) recommended by the printer or printing service is also important.

For this example, we will use 350 dpi, as this is the recommended resolution or higher for printing services for business cards and flyers. The size should be set based on this resolution.

STEP3. Calculate Based on the Number of Cells and DPI

Since dpi = dots per inch (25.4mm), 350 dpi = 13.7795 dpmm (dots per mm). One dot is approximately 0.07mm.

If we fill one cell with 5x5 dots, one cell will be 0.35mm.

Multiplying this by our 29 cells gives a theoretical minimum size of 10.15mm × 10.15mm for this example.

Calculation Example: (25.4 ÷ 350) × 5 × 29 = 10.15mm

Is the Minimum Size Not Enough? Recommended Size and Guideline for QR Codes

The minimum QR code size mentioned above refers to the "theoretically correct printable size," but in reality, the minimum size may not be sufficient.

If you prioritize smooth reading and user experience, it is important to consider the recommended size.

Depends on Scanner Performance

One reason the minimum size may be insufficient is the issue of scanner performance.

Reading a QR code heavily depends on the performance of the scanner or smartphone camera being used.

While the latest smartphones can often read small QR codes without issue, older models or cameras with low resolution may struggle.

Therefore, you might consider a size of 0.5mm per cell or more.

For larger printed materials like flyers and brochures, it would be ideal to make the QR code even larger to improve visibility.

Results from Actual Device Testing

We actually printed the example QR code with a home printer and scanned it with the standard camera of an iPhone XR.

As a result, the QR code printed at the minimum size of 11.6mm was read without any problems.

To be precise, it required a moment to focus, but the reading itself was fine. Since the iPhone XR is an older model, newer models should read it even more easily, so 11.6mm can be considered sufficient.

On the other hand, considering a case where a QR code is placed on a business card, 20mm feels a bit too large. Since it was readable from 11.6mm, we recommend a size between 12mm - 15mm. (The final size decision is your own responsibility.)

The Maximum Size of a QR Code

Conversely, is it better for a QR code to be larger?

In conclusion, as long as it fits within the camera frame of the reading device and the image quality does not degrade, a larger size is not a problem. As an example of a large real-world QR code, they are sometimes displayed in the sky by drones.

Also, if you enlarge a QR code and the image quality is insufficient, causing the dots to become blurry, it may become unreadable. If there's a possibility of enlargement, it is recommended to save it in SVG format, which does not degrade no matter how much it is magnified.

What Versions Can Be Smoothly Read by a Mobile Phones?

The maximum QR code version is 40, which has 177 cells on one side. We actually conducted a reading test of a maximum version 40 QR code using both iPhone and Android smartphones.

What is a QR Code Version?

The result was that both the iPhone and Android were able to read the version 40 QR code.

However, the reading was difficult, and it took several tens of seconds until it could be read, requiring adjustments for lighting and focus.

Therefore, if the reading environment is not consistent, it is better to keep the QR code not too large.

Points of Caution Besides Size When Creating a QR Code

When creating a QR code, there are other important points to consider besides size.

Below is a summary of often overlooked points.

Ensure Sufficient Margins

A QR code requires a sufficient margin (quiet zone) around it. Without this margin, the scanner cannot recognize the boundaries of the QR code, leading to reading errors.

The recommended margin is at least 4 cells' worth of space around the entire code. For example, if the QR code body is 20mm square, the size including the margin should be 28mm square or more.

Ensure Contrast

There must be sufficient contrast between the background color of the QR code and the color of the code itself.

The combination of black and white is the most effective.

If the background is colorful, use a dark-colored QR code. Even when using a colorful design, be careful not to compromise the contrast.

Set a Proper Error Correction Level

QR codes have an error correction level (L, M, Q, H, from lowest to highest), and the higher the level, the more resistant it is to damage and dirt.

For business cards and brochures, which are less likely to get dirty, level "M" or "Q" is common.

For outdoor signs, etc., choosing level "H" is safer to account for dirt and weather.

However, keep in mind that raising the error correction level increases the QR code's data volume and size, so a balance must be struck.

A deep dive into the error correction function is explained here.

Summary: What is the Recommended and Minimum Size for Printing a QR Code?

When creating and printing a QR code, the minimum size should be considered merely a "bare minimum guideline."

To improve readability and visibility, it is important to choose a recommended size with some leeway.

The recommended size guidelines (these are just guidelines) are as follows:

• Minimum size for printed materials: 1 cell = 0.4mm or more, 12mm - 15mm square recommended

• Minimum size for digital environments: 150px × 150px or more, 300px × 300px or more for Retina support

If you want to know the theoretically required minimum size, please check with the procedure we introduced.

However, please note that this is the size required for printing purposes, and whether it can be read successfully also depends on the scanner's performance.

Also, pay attention to points such as ensuring margins, contrast, and the error correction level.

By choosing the appropriate size and design, you can maximize the effectiveness of your QR code.

For creating QR codes and checking their versions, please use QR STOCK!

• Free, no registration required, commercially usable

• Operated by a Japanese company

• Supports QR code creation and reading

• Detailed design customization is also possible

Please give it a try!