How big should a QR code be?
There is no single useful minimum QR code size for every job. A short URL on a business card and a dense QR on a poster can contain different numbers of modules, and the intended scanning distance also matters.
This calculator uses the content you actually intend to encode to determine the QR version and module count, then combines that with the scanning distance and conservative physical-size assumptions.
Use the result as a starting point, not a certification.