Point for setting the module size

Once a symbol version is determined, the actual size of the QR Code symbol depends on the millimeter size of the module (one square area comprising QR Code) to be printed.
The larger the module is, the more stable and easier to read with a QR Code scanner it becomes. On the other hand, as the QR Code symbol size gets larger, a larger printing area is required. It is, therefore, necessary to determine the module size of each application after considering all the relevant factors. It is recommended that QR Code symbols be printed as large as possible within the available printing area.

Printer Head Density and Module Size

Printer and module size
Printer Head density 4-dot configuration 5-dot configuration 6-dot configuration
Laser 600dpi(24dot/mm) 0.17mm 0.21mm 0.25mm
360dpi(14dot/mm) 0.28mm 0.35mm 0.42mm
Thermal 300dpi(12dot/mm) 0.33mm 0.42mm 0.5mm
200dpi(8dot/mm) 0.5mm 0.63mm 0.75mm

* Dot: the minimum picture element making up a rendered image. With printers and image scanners, this is expressed as dpi or dots per inch (dots/inch).

The module size of a standard thermal transfer/direct thermal printer depends on the number of dots in the printer head.*

For example, if the head density is 300dpi and each module is made up of 5 dots, the module size is 0.42 mm/molule. Increasing the number of dots improves printing quality, eliminates printing width or paper feed speed fluctuations, distortion of axis, blurring, etc, and enables more stable operations.
DENSO WAVE recommends for stable operations that each module is made up of 4 or more dots.

Size of module that can be read by scanners

Scanner type Resolution
High resolution type BHT-800Q Series 0.2mm
GT20QD-SM 0.1mm
Standard type BHT-710QWB-CE 0.25mm
BHT-600Q Series
QK20 Series
Camera type QD25 Variable according to lens
Decode software QRdeCODE Variable according to iPhone

Each scanner has its own readable module size limit. The scanner resolution represents this limit.

For example, if a QR Code symbol is printed with a 600 dpi, 4-dot printer, the module size is 0.17mm. A scanner resolution of less than 0.17mm is required to read the symbol.

Small printing in the limited area with a higher head density printer can be useless if the reading limit of the scanner is exceeded.

Consider the scanner to be adopted before determining the module size to be used.

A lineup of the scanners put out by DENSO WAVE is shown on the right (example)