Calculate materials for floor tiling projects, grout, and mortar.
The gap between tiles.
Also sets how deep the grout goes on a floor.
Extra to order for cuts at the walls. 10% is typical, more for diagonal.
Nothing to work out yet
Enter values for Length, Width, Grout Joint Width, Tile Thickness, Tiles per Box.
Floor area divided by the area of one tile gives the raw count, then your waste factor is added and the result rounded up to whole tiles. Grout is worked out as a volume rather than guessed per tile: how much joint runs through a square metre depends on the tile size, and that length is multiplied by your joint width and the tile thickness, then weighed. Small formats such as mosaic carry far more joint per square metre than large ones. Thinset coverage follows the trowel notch for the tile's longest side, so a 24×12 plank is treated as a 24 job, not a 12. Edge trim is the room perimeter, which is where trim, edging or a cut against the skirting runs — taken from the room you already typed rather than asking for it twice.
Five square metres of floor, 12 by 12 inch ceramic, 3 mm joints, laid straight, with a 10% waste factor. The calculator returns 60 tiles, 5 boxes, 1.4 kg of grout, one bag of thin-set and 9 metres of edge trim.
A "12x12" tile is 305 by 305 mm, which is 0.0929 m². Five square metres divided by that is 53.8 tiles, and the 10% waste takes it to 60. The boxes line is the one that matters at the counter: at 12 tiles a box you buy 5 boxes, which is exactly 60 tiles. Tiles are not sold loose, so the number you pay for is always a multiple of the box.
Grout is worked out as a volume rather than guessed. Five square metres of 305 mm tiles contains 32.8 metres of joint; multiply by 3 mm wide and 8 mm deep and weigh it, and you get 1.4 kg. That is why a mosaic floor of the same area needs far more grout than a large-format one — there is simply more joint in it.
Using one waste factor for every layout. A straight grid wastes about 10% because only the perimeter needs cutting. Turn the same floor 45 degrees and every tile at every wall becomes a cut, and the figure climbs. Herringbone is higher again.
The Layout Pattern dropdown tells you what is typical for the pattern you picked, and it never overwrites the waste factor you typed — the advice is there to be taken or ignored, not applied behind your back. The second mistake is ordering the exact count with no allowance at all, which leaves you with no spares for a cracked tile in two years, by which time the batch will have changed shade.
Boxes, not tiles, and the batch matters. Ask for all boxes from the same batch number: ceramic and porcelain shade-vary between production runs, and a floor laid from two batches can show a visible line across it.
Thin-set coverage follows the tile's longest side, because bigger tiles need a deeper notched trowel and a deeper notch spreads less per bag. A 24×12 plank is treated as a 24, not a 12 — the long side is what sets the trowel. Stone is usually back-buttered as well, which uses more again.
The working names the actual tile size in millimetres, so you can check it against the box. Nominal tile names are approximate: a "12x12" is 305 mm because it is a converted 12 inches, and a "600x600" really is 600. If your tile is a genuine 300 mm, use the Custom size option rather than the nearest named one — over a large floor the difference is real tiles.
Edge trim is taken from the room you already typed rather than asked for twice. It is the perimeter, which is where trim, edging, or a cut against the skirting runs.