The three states
Ready to print Print it at least 20 mm (0.8 in) wide. Simple code, 25 × 25.
Test one copy first Print it at least 22.8 mm (0.9 in) wide. Busy code, 49 × 49.
Hard to scan when small Print it at least 40.4 mm (1.6 in) wide, or shorten the content. Very dense code, 93 × 93.
| State | Grid size | What to do |
|---|---|---|
| Ready to print | Up to 33 × 33 | Print at the width shown or larger. |
| Test one copy first | 37 × 37 to 57 × 57 | Print one copy at its real size and scan it with a phone before printing many. |
| Hard to scan when small | 61 × 61 and up | Shorten what is in the code, or print it well above the width shown. |
Each state carries a word and an icon as well as a colour, so it reads the same for everyone.
How the width is worked out
Two rules, and the larger one wins:
- Never below 20 mm (0.8 in). This is the floor our sizing guide sets for any printed code. Below it, even close range scanning gets unreliable on older phones.
- 0.4 mm per module, plus the quiet zone. The width is (modules + 8) × 0.4 mm, where 8 is the 4 module margin on each side. This only goes above 20 mm for codes of 45 × 45 and larger.
The badge is a minimum for scanning up close, around 20 to 30 cm. Codes read from further away need to be bigger. A common rule is one tenth of the scanning distance: a code read from 1 m (about 3 ft) should be about 10 cm (4 in) wide.
Worked examples
| Grid | 0.4 mm rule | Badge shows |
|---|---|---|
| 25 × 25 | 13.2 mm | 20 mm (0.8 in) |
| 41 × 41 | 19.6 mm | 20 mm (0.8 in) |
| 49 × 49 | 22.8 mm | 22.8 mm (0.9 in) |
| 93 × 93 | 40.4 mm | 40.4 mm (1.6 in) |
When to print bigger
- The code will be read from more than an arm's length away.
- It goes on a curved, shiny or textured surface.
- It is printed in colour rather than black on white, or carries a logo.
- The badge says Test one copy first or Hard to scan when small.
The Sign maker sizes codes for common sign formats, and the Stress test shows where a particular code stops scanning.