A QR code that looks sharp on a phone can fail in print: the modules are too small for the scanner, the quiet zone got cropped, or contrast disappeared on dark or glossy stock. This note is for developers generating codes for cards, labels or flyers.

The figures below come from DENSO WAVE, the inventor of QR Code, whose public documentation matches the model in ISO/IEC 18004 (first published as an ISO standard in 2000; current edition 2024). I am not quoting unpublished tables from the standard itself.

Size is module size times module count

A QR Code is a grid of square modules. Once you know the version, printed size is:

printed size = (modules + 2 × quiet-zone modules) × module size

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DENSO WAVE's outline of the specification gives the grid sizes: Version 1 is 21 × 21 modules, growing by four modules per side up to Version 40 at 177 × 177. Version V is 21 + 4 × (V − 1) modules on a side. The payload, not a style option, usually picks the version.…