Sizing calculator
How big should this QR code be?
Paste what the code will contain, choose a print width or a scan distance, and read the answer. The same panel lives inside the generator.
Only used to count modules. It stays in your browser.
Arm's length is about 0.3 m. A poster across a room is 2 to 3 m.
Result
print safe- Version
- 3
- Modules
- 29+8
- Module size
- 1.08mm
- Reads to
- 0.4m
- At 40 mm, each module is 1.08 mm. Safe. Reliable to about 0.4 m.
For a scan distance of 0.3 m, print at least 37.5 mm wide. To keep modules at 0.5 mm, print at least 18.5 mm.
What error correction costs
| ECC | Version | Modules | Min width @0.5 mm |
|---|---|---|---|
| L | 2 | 25 | 16.5 mm |
| M | 3 | 29 | 18.5 mm |
| Q | 3 | 29 | 18.5 mm |
| H | 4 | 33 | 20.5 mm |
Higher error correction survives more damage and logos, but needs more modules, so it needs more paper for the same module size.
The rules behind the numbers
A QR code is a grid of square modules. Version 1 is 21 modules across; each version adds 4, up to 177 at version 40. Around the grid sits a quiet zone of 4 blank modules on every side, which scanners need to find the edges. The printed width is shared between all of those modules, so the more content you encode, the smaller each module gets at a given size.
Phone cameras need each module to cover a few pixels at the distance they scan from. In practice, modules under about 0.4 mm are unreliable in print, and 0.5 mm or larger is comfortable. The other rule of thumb is that a code can be read from about ten times its own width: a 30 mm code from 0.3 m, a 250 mm sign from about 2 m, with a 25 percent margin for poor light and angles built into the recommendation above.
If the calculator says your code is too small, you have three levers: print it larger, encode less (a shorter URL is the usual fix), or lower the error correction. Error correction is worth keeping at M or higher for anything that will live outdoors or wear a logo.