Tile Calculator

Enter the room's length and width and the size of one tile, and the calculator divides area by area, adds a waste allowance for cuts and breakages, and rounds up to whole tiles. Give it the number of tiles per box and it tells you how many boxes to buy. Metric and imperial both work — room in metres with tiles in centimetres, or room in feet with tiles in inches.

Dividing area by area gives a lower bound rather than the answer, and the gap can be large. Tiles are laid in rows, and a row that needs a narrow strip along one wall still consumes whole tiles to cut from. A 3.2 by 2.7 metre room in 60 cm tiles works out to 24 tiles by area, but a grid of six columns by five rows is 30 — twenty-five percent more for the same floor. Reality usually lands between the two, because an off-cut from the left edge can often finish the right edge, but only when the leftover piece is wide enough and the pattern allows it. That is a large part of what the waste allowance is really covering.

Ten percent is the usual default for a straight lay in a simple rectangular room. Push it to fifteen for a diagonal layout or a herringbone, where almost every edge tile is a cut and the off-cuts are triangles that fit nothing else, and push it further for a room with alcoves, a bay window or anything that turns one straight edge into three. If a pattern has to line up across a doorway, add more still.

Two things to settle before ordering rather than after. Buy the whole job in one batch: tiles are fired in lots and the shade drifts between them, enough to see as a band across a floor when a later box is opened to finish a corner. And measure the tile rather than trusting its name — a tile sold as 60 by 60 is often 597 mm, sized so that a 3 mm grout joint brings the repeat to exactly 600. Using the nominal figure to plan a run of ten tiles quietly loses three centimetres.