On this page: The 10:1 rule · Size table · Why density changes the answer · Thinking in modules · Choosing an export size
The 10:1 rule
Print the code at least one tenth the width of the distance it will be scanned from. That is the rule of thumb used across the industry, and it is a good starting point because it scales sensibly: closer viewing needs a smaller code, further viewing needs a bigger one.
A QR code read from 30 cm — a table tent, a till receipt, a business card handed across a desk — needs to be about 3 cm wide. A code read from 3 metres — a poster on a wall, a window decal — needs to be about 30 cm wide.
Treat it as a floor, not a target. Two adjustments almost always push you larger:
- Dense payloads need more. A code carrying 100 characters needs a bigger physical size than one carrying 20, because it has more modules to fit into the same area. See the density section below.
- Real-world conditions are worse than ideal. The rule assumes a clean, well-lit, flat, matte surface and a modern phone. Print on a curved bottle in a dim bar and you want double the size for the same reliability.
Print size table
These are practical minimums for a short payload — a link, a Wi-Fi network, a phone number. Add roughly 50% for a contact card or anything with more than about 60 characters.
| Placement | Typical scan distance | Minimum width | Comfortable width |
|---|---|---|---|
| Business card | 20–30 cm | 2 cm | 2.5 cm |
| Event badge, name tag | 25–35 cm | 2 cm | 3 cm |
| Product label, small packaging | 25–40 cm | 2.5 cm | 3 cm |
| Table tent, coaster, menu insert | 30–50 cm | 3 cm | 4 cm |
| Receipt or invoice footer | 30–45 cm | 3 cm | 3.5 cm |
| Postcard, flyer | 30–50 cm | 3 cm | 4 cm |
| Counter standee | 1–2 m | 10 cm | 15 cm |
| Guest room wall card | 1–1.5 m | 10 cm | 15 cm |
| Poster, A3 and smaller | 1.5–2.5 m | 15 cm | 25 cm |
| Shop window decal | 2–4 m | 20 cm | 40 cm |
| Large poster, A1 and larger | 3–5 m | 30 cm | 50 cm |
| Billboard, roadside | 10 m or more | 1 m | 2 m or more |
Widths refer to the code's own edge-to-edge measurement. The quiet-zone margin sits outside that measurement and must be kept clear as well.
Why density changes the answer
The 10:1 rule does not know how much data your code carries, which is why it can mislead. What actually matters to a camera is not the code's outer size but the size of an individual module — one of the small squares in the grid.
A QR code's grid grows with its payload. A short link might be version 3, a 29×29 grid. A contact card with several fields might be version 12, a 65×65 grid. Print both at 3 cm wide and the first has modules about 0.9 mm across while the second has modules about 0.4 mm across. The second is far more likely to fail.
The rule of thumb that follows: halving the module size requires doubling the print size to get the same reliability.
Working out module size
You do not need to count squares by hand. QRMint shows the module count and version in the preview panel as you type. Take the printed width and divide by the module count:
module size = printed width ÷ module count
For dependable scanning on a typical phone, aim for a module size of about 0.5 mm or larger. Below about 0.3 mm, expect failures on anything but a flagship camera held very steady in good light.
Two worked examples:
- Version 3 (29 modules) printed at 30 mm: 30 ÷ 29 = 1.03 mm per module. Very comfortable.
- Version 12 (65 modules) printed at 30 mm: 30 ÷ 65 = 0.46 mm per module. Scannable, but close to the limit — this is where a longer URL starts to bite.
That is the concrete reason a contact card should carry fewer fields, and why shortening a URL before printing is worth the extra step. Both reduce the module count, which increases the module size at a fixed print size.
Thinking in modules
Three module-level rules govern whether a printed code works, and all three are independent of the distance rule.
- The quiet zone is four modules minimum. Not four millimetres — four modules. A dense code therefore needs a proportionally wider blank border than a sparse one.
- A module must not merge with its neighbour. If ink spreads, or a laser printer cannot resolve the grid, adjacent dark modules blur into one and the data changes. This is why very small codes fail on cheap printers regardless of the file's quality.
- Squarer codes scan better than the maths suggests. Always keep the aspect ratio 1:1. A stretched code is a common mistake in design software — it looks fine and decodes badly.
Choosing an export size
For digital use, the export size in pixels matters more than any physical measurement, because the image will be scaled by whatever displays it.
| Use | Recommended export | Why |
|---|---|---|
| Small on-screen icon, email signature | 512 px PNG | Plenty for a display size under 200 px wide, even on a high-density screen. |
| Website, social media, presentations | 1024 px PNG | The safe default. Survives scaling and cropping without softening. |
| Large display, digital signage, slide on a projector | 2048 px PNG | Keeps modules crisp when shown large. |
| Anything going to a printer | SVG | True vector art. Resolution is set by the press, so it stays sharp at any size. |
| Printing an A4 sheet yourself | Pre-sized to the page, ready to print without scaling. |
Prefer SVG whenever a professional printer is involved. A PNG has a fixed number of pixels; if the printer needs it larger, they must interpolate, and interpolated module edges are soft. SVG has no fixed resolution, so the press decides.
One note on print resolution: if you must supply a raster file to a printer, send it at 600 DPI at the final printed size rather than a fixed pixel count. A 3 cm code at 600 DPI is about 709 px, which is why a "large" 4096 px PNG is often unnecessary — but it never hurts.
The short version
- Minimum width = scan distance ÷ 10. For 3 m, that is 30 cm.
- Never go below 2 cm for print, regardless of payload.
- Halve the module size and you must double the print size.
- Target a module size of 0.5 mm or more; 0.3 mm is the danger line.
- Keep four modules of clear margin on every side — always.
- Send SVG to printers. Use 1024 px PNG as your screen default.
Related reading
- Why QR codes fail to scan — the four causes, diagnosed.
- Design that still scans — colour, gradients, shapes and logos.
- Choosing the right QR code type — shorter payloads scan more easily.