QR Code Size Calculator

What it works out

How big a QR code needs to be printed for a given scanning distance, and what that means in millimetres, inches and pixels at your print resolution. It also reports the module size, which is the number that actually decides whether a printer can hold the detail.

Paste the real content

Size depends on how much data is in the code, so the calculator encodes the content you type and uses the resulting module count. A short link and a full vCard need very different sizes at the same distance. Change the error-correction level too — H adds redundancy and therefore modules.

The rule behind the number

The estimate uses the widely applied field rule that a phone can read a code from roughly ten times its width, tightened to eight for dense codes and relaxed to twelve for sparse ones. It is a planning heuristic, not a specification: real performance depends on the camera, the lighting, the substrate and how steady the hand is. Treat the output as a recommended estimate and test a printed sample.

Do not forget the quiet zone

The QR specification asks for four modules of clear space on every side. The calculator reports the size with and without it. Losing the quiet zone to a border, a fold or a busy background is one of the most common reasons a technically perfect code fails in the field.

The floor

Below about 20 mm across, phone cameras struggle regardless of the arithmetic — focus distance and sensor resolution stop cooperating. If the maths says 12 mm, print 20 mm.

Then test it

Print at the final size, on the final material, and scan with a few real phones including an old one. The testing guide sets out a repeatable routine worth following before any print run.

Where the numbers come from

The estimate uses the field convention that a phone camera reads a QR code from roughly ten times the code's width — a 25 mm code at about 250 mm, a 100 mm code at about a metre. This tool refines that by symbol density, because a dense code has smaller modules at the same overall size:

This is a planning rule of thumb, not a specification. It is not from ISO/IEC 18004, which specifies the symbology rather than viewing distance. Real performance depends on the camera, the lighting, the print and whether the person scanning holds still — so treat the answer as a starting size to test, and round up rather than down.

Below about 20 mm, phone cameras struggle regardless of the arithmetic. Fixed-focus and older cameras cannot resolve modules that small. Treat 20 mm as a floor for anything the public will scan, and 25 mm as a comfortable minimum for print.

Add the quiet zone to the space you allow

ISO/IEC 18004 requires four clear modules on every side. That is not part of the width the calculator gives you as the symbol size — the second figure includes it, and that is the one to design your layout around.

On a 33-module code the quiet zone adds 8 modules, about 24% to the overall width. A 30 mm symbol needs roughly 37 mm of clear space. Squeezing a code into a box exactly its own size removes the quiet zone and is one of the most common reasons a printed code fails while the digital file scans perfectly.

Print resolution, and screens

The pixel figure converts the physical size at your chosen DPI. Some practical values: 300 dpi for commercial print, 150 dpi for large-format material viewed from a distance, 203 or 300 dpi for a thermal label printer, 72–96 dpi for screen.

Where possible download SVG instead. It is a real vector, so it is sharp at any size and there is no resolution to get wrong. Use PNG when the destination cannot take vectors, and generate it at the final size rather than scaling a small PNG up.

For a code shown on a screen — a slide, a shop display, a TV — the ten-times rule still applies to the physical size on that display, not to its pixel dimensions. Measure the screen with a ruler and work from that. Also allow for the viewer's angle: a code at the far edge of a wide display is being read obliquely, which costs effective resolution.