QR code size for a poster

Match the size to the placement

A "poster" spans everything from an A4 sheet on a noticeboard to an A0 sheet across a lobby, and the code size follows the viewing distance, not the paper size:

Placement	Viewing distance	Minimum code	Typical format
Noticeboard, read face-on	50 cm	5 cm	A4
Corridor wall	1 m	10 cm	A3
Room wall at eye level	2 m	20 cm	A1
Lobby, stage backdrop	3 m	30 cm	A0 or larger

A 10 cm code on an A4 poster looks enormous — nearly half the width. Print it anyway. An oversized code costs a little elegance; an undersized one costs every scan. Most poster codes in the wild are 2–3 cm, sized for a flyer in the hand rather than a wall at 2 m, which is why they go unscanned. The arithmetic behind the ratio is in the ten-to-one rule.

Mounting height is part of the distance

The 10:1 measurement is camera-to-code, not viewer-to-wall. Put a code at the top of an A1 poster whose centre hangs at 1.9 m and a viewer standing 2 m back with eyes at 1.6 m is actually about 2.2 m from the code — and looking up at it, so the modules foreshorten vertically. Both effects spend margin you wanted for lighting and focus.

The fix costs nothing: place the code in the poster's lower half, between 1.2 and 1.7 m off the floor, face-height for someone standing close. Where that fights the layout, follow the guidance in QR placement in a layout rather than shrinking the code to fit a corner.

Payload and error correction

• EC M is the default for posters; use EC H only when a logo sits in the code, since the extra redundancy raises the version and shrinks modules at a fixed size.
• Keep the URL short. A 25-character URL at EC M is a 25-module code; at 20 cm printed width each module is a generous 8 mm.
• Give the code a caption that says where it leads. A poster is read in passing, and a clear call to action decides whether anyone stops for the three seconds a scan takes.

Surface-specific advice — paper stocks, mounting, indoor vs outdoor — lives on the posters surface page; the outdoor durability guide covers laminates and sun. For sizing, run your payload and distance through the size calculator, and check the artwork decodes before the print run.

FAQ

How big should a QR code be on a poster?

One tenth of the viewing distance — 5 cm for a noticeboard at 50 cm, 10 cm for a corridor at 1 m, 20–30 cm for a wall read from 2–3 m. Most poster codes are printed far smaller than this and are never scanned.

How big should a QR code be on an A4 poster?

If the poster hangs where people stand about a metre away, 8–10 cm. That is close to half the sheet's width, which looks large but is what the distance demands.

Where should a QR code go on a poster?

In the lower half, roughly 1.2–1.7 m off the floor once hung, with the full quiet zone kept clear. Codes placed high on the sheet gain distance and angle that the sizing maths then has to absorb.

What error correction level should a poster QR code use?

M, unless a logo overlays the code, in which case H. Higher error correction raises the module count, so on a fixed-size code it shrinks every module — the opposite of what distance scanning needs.