Tile Calculator

How a tile count is actually worked out

Every tile estimate is the same three-step calculation. Work out the area you are covering, add a waste allowance for cuts and breakage, then divide by the face area of one tile and round up. The rounding matters more than people expect: you cannot buy 0.4 of a tile, and the offcut left over from trimming a tile at the wall almost never fits the next gap, so partial tiles do not carry forward the way the arithmetic implies.

The one thing that trips up most DIY estimates is mixing units. Tile is sold in inches or centimetres while rooms are measured in feet or metres, so a 12 by 12 inch tile is not 12 square feet, it is one. This calculator converts the tile face into the same unit as your room before dividing — inches to square feet by dividing by 144, centimetres to square metres by dividing by 10,000.

Worked example: a 10 x 8 ft bathroom floor in subway tile

The floor is 10 ft by 8 ft, which is 80 sq ft. Add the standard 10 percent allowance and you are buying for 88 sq ft. A 3 by 6 inch subway tile has a face of 18 square inches, or 0.125 sq ft, so 88 divided by 0.125 gives 704 tiles. If the box holds 80 tiles, that is 8.8 boxes, which rounds to 9 boxes and 720 tiles — 16 spares to put in the loft for future repairs. Small-format tile always produces big counts, which is why the box figure is the number that really tells you what the job costs.

Worked example: the same room in 12 x 24 large format, laid diagonally

Diagonal layouts push the allowance to 15 percent, so 80 sq ft becomes 92 sq ft. A 12 by 24 inch tile covers 288 square inches, exactly 2 sq ft, so you need 46 tiles. At 8 tiles per box that is 5.75 boxes, rounded up to 6 boxes, or 48 tiles. Compare that with the subway option: same floor, same room, 704 tiles versus 46. Format choice changes the labour more than the material cost, since every tile is a separate placement, spacer set and grout line.

Worked example in metric: a 4.2 x 3.6 m kitchen

That floor is 15.12 m². With a 10 percent allowance you are covering 16.63 m². A 60 by 60 cm tile has a face of 0.36 m², so 16.63 divided by 0.36 is 46.2, rounded up to 47 tiles. Boxes of four give 11.75, so you buy 12 boxes — 48 tiles. Notice how the box rounding quietly adds material twice; ordering slightly more than the raw tile count is normal, not an error in the estimate.

Choosing the waste allowance

The allowance is not padding for its own sake. Every cut at a perimeter turns one tile into one usable piece plus scrap, and rooms that are out of square produce a tapering cut row where each tile is a slightly different width — no two offcuts interchange. Patterned tiles with a directional design lose more again, because you cannot rotate a piece to make it fit.

Dye lots: the reason to order everything at once

Ceramic and porcelain tiles are fired in batches, and the glaze colour drifts measurably between batches. Manufacturers print a shade or calibre code on the carton for exactly this reason. Two boxes from different lots can look identical in the shop and obviously different under bathroom lighting once they are on the wall. Order the full quantity in a single purchase, check that every carton carries the same lot code before you start, and keep the spares from that same lot. A repair tile bought three years later will match nothing.

What this estimate does not cover

The calculation assumes a rectangular field with a simple layout. It does not subtract fixed obstructions such as a kitchen island, a bath tub footprint or cabinet runs — if those are large, measure the covered area separately and use the direct-area mode. It also ignores grout joint width, which slightly reduces the true count and therefore keeps the estimate on the safe side, and it does not price trim pieces, bullnose edging, thresholds, adhesive or grout, all of which are sold by different units. For walls, remember that the visible field usually stops behind fittings, so measure to the actual tile line rather than to the ceiling.

Finally, treat the box figure as the real answer. Retailers rarely split cartons, so the number of boxes is what you pay for, and the leftover tiles inside that last box are the cheapest insurance in the whole project.