The size of a QR code depends on several factors, including the amount of data it contains, the scanning distance, and the viewing environment. For instance, a QR code on a billboard, which will be viewed from a distance, needs to be significantly larger to ensure readability. Conversely, a QR code printed on a product package can be smaller since it will be scanned from a closer distance. It's essential to consider the viewing distance when determining the appropriate size of a QR code to ensure it remains scannable and functional across different scenarios, whether on large-scale advertisements or small product labels. Generally a good rule of thumb is no smaller than 2cm x 2cm (or .8" x .8").
