Estimates only. Always confirm against the tiler's own take-off before ordering — odd-shaped rooms, niches and feature strips change the count. The PDF report opens a print view; choose "Save as PDF" as the destination.

The number that runs you short

The most common tiling mistake on a DIY job is not measuring the room wrong. It is ordering the exact area and nothing else. Tiles get cut at every wall. A few crack on the saw. One arrives chipped in the box. And the day you finally need to replace a damaged tile in five years' time, the shop no longer stocks that colour. The calculator above bakes a wastage margin into the count, but the margin you pick is a judgement call — and a 10% default is not right for every job.

Why the grout joint changes the maths

A 600 mm tile laid with a 3 mm joint does not occupy 600 mm of floor. It occupies 603 mm — the tile plus one joint. Across a room that adds up to a measurable amount of space, which means you need slightly fewer tiles than a naïve area-divided-by-tile-area sum suggests. Plenty of online calculators skip this entirely. This one includes the joint, so widening your grout lines will nudge the tile count down. It is a small effect on a small tile and a real one on large-format tiles with wide joints.

Wastage is not one number

Trade rule of thumb, and the advice most tile suppliers give, runs roughly like this: around 10% for a straight or brick-bond layout, about 15% once you go diagonal, and 15–20% for herringbone because the pattern forces a cut tile at every edge. Add more, not less, when the room is small, when there are lots of obstacles to cut around, or when the tile is large-format and a botched cut wastes a big piece. The calculator suggests a figure when you pick a pattern; treat it as a floor, not a ceiling.

The batch number nobody mentions

Ceramic and porcelain tiles are fired in batches, and shade varies between them — the box will carry a batch or "shade" code for exactly this reason. Buy every tile for the job, including the spare box, in one order from one batch. A box bought months later can sit a shade off and show as a patch under the light. Keep that spare box after the job too. Australia's tiling installation standard, AS 3958.1, and the Tile Council of North America (TCNA) Handbook both treat allowance for waste and cuts as standard practice rather than optional.

Boxes, not tiles

Shops sell tiles by the box, so the real order quantity is always rounded up to a whole box. As a rough guide, large-format tiles come around 2 to a box, 600 mm tiles about 4, 300 × 600 mm tiles 6 to 8, and 300 mm tiles 9 to 12 — wall tiles are thinner and often pack a few more. Enter the figure from the product page and the calculator rounds for you.

Working in old-fashioned units, or need to convert a room measured in feet to metres before you start? The unit conversion tool handles length, area and volume. There is more in the measurements section and the home & DIY hub, or take a chance with a random page.