Surface guide
QR codes on posters
A poster QR code is read from between one and three metres, so under the ten-to-one rule it needs to be 10–30 cm wide. Most posters carry codes at 3–5 cm, which is why most poster codes go unscanned.
| Typical scan distance | 1–3 m |
|---|---|
| Minimum code width | 10–30 cm |
| Error correction | M |
The numbers
| Viewing distance | Minimum code width |
|---|---|
| 1 m (a corridor poster) | 10 cm |
| 2 m (a wall at eye level) | 20 cm |
| 3 m (across a lobby) | 30 cm |
That is the code, not the frame or the caption. On an A3 poster a compliant code occupies roughly a quarter of the sheet — which is exactly why designers shrink it, and exactly why it then fails.
The real constraint is dwell time, not size
Nobody stops in a corridor to scan a poster. The codes that work are where people already wait: a lift lobby, a bus shelter, a queue, a toilet door. Put a code where the audience is stationary for thirty seconds and a 10 cm code outperforms a 30 cm one on a wall people walk past.
Height matters more than people think
Centre the code at 1.4–1.6 m from the floor. Above 1.8 m the scan angle exceeds about 40° for anyone standing close, and steep angles are where decoding fails first.
Print notes
- Matt stock. Gloss under downlighting produces specular reflection across the whole code, and no error-correction level survives that.
- Print from SVG or PDF, never an upscaled PNG.
- Error correction M is right. Codes this large have huge modules; H just wastes area.
- Give the four-module quiet zone real white space — poster designs habitually crowd it.