Tiles cannot be ordered by area alone. A tiled surface is laid in whole rows and whole columns, and what you need is a piece count to convert into boxes. Enter the room's length and width, the tile's width and height, a waste percentage and the tiles per box, and the calculator returns tiles across, tiles down, the total piece count including waste, and the boxes to order.
Area and count disagree, and that is the point. A 4 m × 3 m floor is 12 m²; divide by the 0.18 m² of a 30 × 60 cm tile and you get 67. But the last column and the last row are cut from whole tiles, so the count is 70. Ordering on area leaves you short.
Room dimensions are entered in metres (or feet) while tile dimensions are entered in centimetres (or inches). Those are different scales, so the tool converts both to a common base before dividing — the room from metres or feet, the tile from centimetres or inches. Dividing a room in feet by a tile in inches directly is the classic way to overstate a tile count roughly threefold, which is why the conversion is explicit rather than implicit.
tiles across = room length ÷ tile width, rounded uptiles down = room width ÷ tile height, rounded uptiles = tiles across × tiles downtiles with waste = tiles × (1 + waste ÷ 100), rounded upboxes = tiles with waste ÷ tiles per box, rounded upTwo choices are deliberate. Each direction rounds up separately, which is what forces the extra tile at the end of every row and column. And no grout joint is added to the tile module: a 3 mm joint makes each tile occupy slightly more floor, so a joint-aware count would come out marginally smaller. Ignoring joints means the calculator can only over-count, never under-count.
A bathroom floor 4.2 m by 3.1 m, with the 30 cm edge running along the long wall, 10% waste and boxes of 4.
| Step | Calculation | Result |
|---|---|---|
| Tiles across | 4.2 ÷ 0.30 = 14.0, rounded up | 14 |
| Tiles down | 3.1 ÷ 0.60 = 5.17, rounded up | 6 |
| Piece count | 14 × 6 | 84 tiles |
| Waste at 10% | 84 × 1.10 = 92.4, rounded up | 93 tiles |
| Boxes of 4 | 93 ÷ 4 = 23.25, rounded up | 24 boxes |
Rotate the same tile 90°, so 60 cm runs along the 4.2 m wall: across becomes ceil(4.2 ÷ 0.60) = 7 and down becomes ceil(3.1 ÷ 0.30) = 11, giving 77 tiles, 85 with waste and 22 boxes. Same room, same tile, two boxes of difference.
Note the 5.17 as well. Five whole 60 cm tiles cover 3.0 m of a 3.1 m wall, so the sixth row is a 10 cm sliver running the length of the room. Centring the layout leaves two cuts of roughly 20 cm instead, uses the same number of tiles, and looks intentional. The calculator counts tiles, not aesthetics.
Waste has to reflect the cut pattern. Straight lay in a plain room typically wants 5–10%; a diagonal or diamond lay typically 10–15%; herringbone typically 15–20%. The per-direction round-up is already inside the count, and the waste percentage sits on top of it.
Whole rows assume a whole rectangle. Nothing is subtracted for a doorway, shower tray, vanity unit or pillar. In a bathroom those often cancel out — tiles gained where the tray sits, lost again to the cuts around it — but in a large room with a big fitted unit they do not.
Boxes are the order, tiles are the count. You cannot buy 93 tiles if the box holds 4; you buy 24 and hold 3 spares, and a later batch will not match. Tiles are fired in batches and tone varies visibly under a bathroom light, so order every box in one go, check the batch numbers agree, and leave time either side of the job — adhesive cures before grouting, and grout cures before the floor is walked on.
Because tiles are whole objects. If the room is 5.17 tiles across, the last row is cut from a whole tile, so six tiles are consumed across that direction and the offcut is generally unusable elsewhere.
Enter the nominal tile size, which is what the box states. The tool adds no joint allowance at all, so a few millimetres of grout only ever reduce the true count relative to the estimate.
No. Wall tiling usually carries more waste than the floor of the same room, because sockets, extractor vents and a window force cuts in the middle of a run as well as at the edges.
One box from the same batch. It covers a cracked tile during the job and a replacement years later, and tiles are frequently discontinued long before a floor wears out.
Room dimensions in feet, tile dimensions in inches. A 13 ft × 10 ft floor in 12 in × 24 in tiles takes 13 tiles across and 5 down, so around 65 tiles before waste. Checking the count against the floor area is the quickest sanity test, and the two always agree: 130 ft² of floor at 2 ft² per tile is 65 tiles. If the area check and the row count disagree, a field has been filled in the wrong unit.