Created Quick Response Code today using the QR Codify website:
This image is 4.843 inches x 4.843 inches. The website downloads the code at 96 dpi but I changed it to 300 dpi at same physical size.
I submitted image to printer as pdf file.
This image embedded here is gif file at 96 dpi:
To know the ideal size, use the following simple formula:
Size of your QR Code = Distance between the QR Code and the Scanner ÷ 10
Example : 33cm square to read it at 3m away.