The module: the key piece
A QR code is a grid of little squares called modules. The smallest QR (version 1) is 21 × 21 modules, and each version adds 4 modules per side: a short link usually takes 25 to 33 modules per side. What decides whether your printer can reproduce the code is not the total size but how big each module is.
With a standard 0.4 mm nozzle, a module under 1 mm prints with rounded edges and the dots merge. As a practical rule:
| Module size | Usual result |
|---|---|
| Under 1 mm | Dots merge: often won't scan |
| 1 to 1.5 mm | Works with good calibration and contrast |
| 1.5 to 2.5 mm | Safe: scans first time almost always |
Recommended sizes
For a short link (about 25–33 modules per side) and high error correction, these sizes work well:
| Object | Code width | Why |
|---|---|---|
| Keychain | 40–50 mm | The reasonable minimum; use a very short link |
| Coaster | 70–80 mm | Scans from the table without leaning in |
| Table stand | 70–90 mm | Comfortable from a chair |
| Wall plate | 100–150 mm | Scanned standing, from further away |
The distance rule
A widely used rule of thumb: maximum scanning distance is about 10 times the code width. A 5 cm QR reads comfortably at about 50 cm; a 10 cm one, at a meter. If your plate goes on a wall and people scan it from afar, make it bigger.
The shorter the link, the fewer modules and the bigger each one gets at the same overall size. Use a short link (for example your Google profile link or a URL shortener) before printing a keychain.
Don't forget the quiet zone
The code needs a plain border around it, the quiet zone. The QR standard recommends 4 modules on each side. Without it, the phone can't tell where the code starts. Our generator already leaves this border on the base of the part.
Error correction: your insurance
QR codes store redundant data so they can be read even if part is damaged. There are four levels: L (7 %), M (15 %), Q (25 %) and H (30 %). For 3D printing use a high level, especially with a logo in the center, since the logo covers part of the code. A higher level adds modules, so compensate with a bit more size.
Quick summary
- Module of 1.5 mm or more with a 0.4 mm nozzle.
- 4 modules of plain margin around it.
- Reading distance ≈ 10 × the width of the code.
- Short link = simpler code = prints better.
Frequently asked questions
What is the minimum size of a 3D-printed QR code?
It depends on the number of modules, but with a 0.4 mm nozzle each module should be at least 1.5 mm. For a short link that means about 40–50 mm wide on a keychain.
From how far can it be scanned?
As a rule of thumb, up to about 10 times the code width: a 5 cm QR reads at about 50 cm.