Physical size vs pixels
Physical size (millimeters or inches) is what a phone camera sees in the real world. Pixel dimensions are a raster export property. Confusing the two is a common print failure mode: a 2000×2000 PNG scaled down to 15 mm on a card still has tiny modules.
For print rasters, pixels and physical size are linked through DPI. SVG exports do not have a fixed pixel resolution; they scale with layout. Choose physical size for scanning conditions, then choose a format and DPI that preserve sharp modules at that size.
pixels ≈ inches × DPI
pixels ≈ (mm / 25.4) × DPI
Modules and QR version
A QR symbol is a square grid of modules. Version determines how many modules sit on each side. At a fixed physical width, a denser matrix shrinks each module—camera focus, print blur, and compression hit small modules first.
- Version 1 → 21×21 modules
- Version 5 → 37×37 modules
- Version 10 → 61×61 modules
- Higher error correction or longer payloads can force a higher version (denser grid) for the same content family
matrix size (modules per side) = 21 + 4 × (version − 1)
| Situation | What happens | Practical response |
|---|---|---|
| Short URL, ECC H | Lower version, larger modules at a given print size | Often fine at modest card/sticker sizes |
| Long URL or contact payload, ECC H | Higher version, smaller modules at the same print size | Increase physical size or shorten the payload |
| Logo + dense payload | Fewer recoverable modules under obstruction | Enlarge print size and test more carefully |
Scanning distance
As scanning distance increases, the QR subtends a smaller angle on the camera sensor. A code that works at arm’s length on a table tent can fail across a room if it stays the same physical size.
A practical planning habit: estimate the farthest realistic scan distance, then size so the full symbol (including quiet zone) remains easy to frame. When in doubt, err larger for posters, window clings, and storefront placements.
- Hand-held / table (roughly 20–40 cm): business-card and sticker sizes are often workable if density is modest
- Standing at a counter or menu board (roughly 0.5–1 m): prefer larger artwork and generous quiet zone
- Across a room or aisle: scale up aggressively; verify with phones at that distance after print
Practical starting points
QRburst Print Studio ships purpose presets that are useful defaults for common jobs. Adjust upward for dense payloads, logos, glossy materials, or longer scan distances.
| Context | Starting width | Notes |
|---|---|---|
| Business card | ~28 mm | Keep payloads short; avoid large logos |
| Sticker | ~30 mm | Watch material glare and edge trim into quiet zone |
| Packaging | ~35 mm | Curves and wraps reduce effective module size |
| Flyer | ~40 mm | Good general handout default at 300 DPI |
| Restaurant table | ~50 mm | Often scanned at arm’s length under mixed lighting |
| Storefront | ~150 mm | Distance-driven; lower DPI may be fine if modules stay large |
| Poster | ~200 mm | Test from intended viewing distance after print |
Common mistakes
Most “too small” failures are really density, quiet-zone, or print-resolution failures wearing a size costume. Fix the constraint that actually broke the scan.
- Shrinking a high-resolution PNG into a tiny layout box (pixels ≠ physical size)
- Encoding a long tracking URL when a short destination would drop version and enlarge modules
- Cropping or decorating into the quiet zone to “save space”
- Matching a competitor’s tiny code without matching their short payload and scan distance
- Skipping a physical proof because the on-screen preview looked sharp