# QR codes on coasters

> A coaster code is read from 40–60 cm on the table, or 25 cm once picked up, so 2.5–4 cm is the working range. Use error correction Q and a waterproof finish — condensation rings soak absorbent pulpboard, spreading ink and warping modules, which is the coaster-specific failure.

Source: https://useqr.app/qr-codes-on/coasters · Last reviewed 2026-08-21 · UseQR is free forever, MIT licensed, no signup.

---

| Typical scan distance | **25–60 cm** |
|---|---|
| Minimum code width | **2.5–4 cm** |
| Error correction | **Q** |

## The numbers

The [ten-to-one rule](/docs/print/the-10-to-1-distance-rule) gives two honest answers,
because a coaster is a hand-held object that starts life on the table:

| Situation | Distance | Code width |
|---|---|---|
| Picked up and held | 25 cm | 2.5 cm |
| Scanned in place on the table | 40–60 cm | 4–6 cm |

On a standard 9–10 cm coaster, a **4 cm** code covers both cases and still leaves room
for artwork. Go below 2.5 cm and nothing saves you. Check your own layout with the
[size calculator](/size-calculator).

## Condensation is the failure mode

This is the surface where water kills codes. A cold glass sheds a ring of condensation
straight onto the coaster, and standard pulpboard — the absorbent stock beer mats are made
from precisely so they soak up drips — wicks it through the print:

- Water-carried ink **spreads**, closing the white gaps between modules.
- The board **swells and warps**, bending the module grid out of plane.
- Repeated wet–dry cycles leave tide-mark stains across the code.

Error correction **Q** absorbs the early damage — that is why it is the specification —
but no correction level survives a fully soaked mat. The production answer:

- **Laminated or varnished coaster board** for anything meant to last a shift; the
  [laminate effects page](/docs/print/laminate-and-varnish-effects-on-scanning) covers the
  glare trade-off (choose matt).
- **Fired ceramic or slate coasters** for permanent installations — the code is glaze, not
  ink, and is immune to water, as with [mugs](/qr-codes-on/mugs).
- Accept that bare pulpboard mats are **disposables**: fine for a two-week promotion,
  wrong for the permanent menu link.

On absorbent stock, keep modules **≥ 1 mm** and contrast at solid black on white — the
**40% luminance-difference** floor degrades fast once the surface stains.

## What coaster codes are for

The coaster's advantage is dwell time: the reader is seated, drink in hand, for half an
hour. The uses that fit: the [menu](/menu-qr-code) or drinks list, a pub-quiz answer
sheet, the venue playlist, and a [review prompt](/google-review-qr-code) — patterns
collected under [QR codes for bars](/qr-codes-for/bars) and
[cafés](/qr-codes-for/cafes). Put the code on **both faces**; coasters get flipped.

## FAQ

### What size should a QR code be on a coaster?

Four centimetres is the safe answer — it scans in place from a seated position at
40–60 cm. The absolute floor is 2.5 cm, which relies on the drinker picking the coaster
up to scan it at hand distance.

### Why did my coaster QR codes stop scanning after one evening?

Condensation. Cold glasses shed water rings, absorbent pulpboard wicks the moisture
through the print, ink spreads and the board warps. Use laminated board or ceramic for
codes that must outlive a single session, and error correction Q for margin.

### What are QR codes on coasters used for?

Menus, pub-quiz entry, playlists and review requests — anything that benefits from a
seated reader with time to spare. A coaster gives you more dwell time than any poster,
which is why scan rates on them beat wall signage.

### Should coaster QR codes be printed on both sides?

Yes. Coasters get flipped, stacked and spun, and whichever face is up is the only one
that exists. Duplicating the code doubles the chance the scannable face is showing when
the drinker gets curious.

## Try it

- https://useqr.app/url
- https://useqr.app/menu
- https://useqr.app/size-calculator
- https://useqr.app/validate