Tile Calculator
How many tiles and boxes a floor or a wall takes, from its size, the tile size and the grout joint, with waste for the layout.
Floor or wall
Tile
Tiles with waste
91
12" × 24" tiles · 16 boxes · 168 ft²
- Area
- 168 ft²
- Tile face
- 2 ft²
- Tiles with waste
- 91
- Boxes
- 16
- Costboxes × price per box
- 672.00
Kalku is coming to iPhone and Android
In the app the tiles are laid out in 3D on the floor you entered, as you type, and the grout, self-leveller, laminate and carpet calcs are next to it. Save the job with a note, share it as a PDF with the shop, and work with no signal.
How it is worked out
A tile covers more than its own face: it covers its share of the grout joints around it. So the calculator adds the joint to the tile's width and to its length, multiplies them for the area one tile really covers, and divides the surface by that. Then it adds the waste allowance and rounds up to whole tiles, and divides by the pieces in a box, rounding up again. This is the Kalku app's Tile & Flooring calc.
Waste is cuts, breakage and the odd tile with a flaw. A straight lay in a rectangular room wastes least; a diagonal lay cuts a tile at every edge, and herringbone more again, which is why the usual allowances step up from 10% to 15% to 20%.
Worked example: a 14 × 12 ft floor in 12 × 24 inch tiles
- Floor: 14 ft × 12 ft = 168 ft², which is 24,192 in².
- Each tile with 1/8" joints covers 12.125 × 24.125 = 292.5 in².
- Tiles: 24,192 ÷ 292.5 = 82.7; with 10% waste, 91.0, so 91 tiles.
- Boxes of 6: 91 ÷ 6 = 15.2, so 16 boxes; at 42 a box, 672.
Walls and splashbacks
A wall works the same way: its width and height are the length and width. Work out each wall on its own, and leave out windows and the space behind a bath or cabinets. Trim pieces, edge profiles and bullnose are counted by length rather than by area; measure them along the edges.
Questions
How much extra tile should I buy?
The calculator starts at 10%, enough for a straight lay with ordinary cuts. Allow about 15% for a diagonal layout and 20% for herringbone or a room with many cuts. Keep a few spare tiles from the same batch: a replacement from a later batch may not match.
Why does the grout joint matter?
Each tile covers its own face plus its share of the joints around it. A 12 × 24 inch tile with 1/8 inch joints covers a 12-1/8 × 24-1/8 inch patch, about 1.6% more than the tile alone. Leave the joint out and the count comes out slightly high; with small tiles and wide joints the difference is much bigger.
How many 12 × 12 tiles in a square foot?
Without joints, exactly one. With 1/8 inch joints each one covers 12-1/8 inches square, so a square foot takes 0.98 of a tile: a 10 × 10 foot floor takes 98 tiles before waste rather than 100.
What if I buy tiles loose rather than by the box?
Set Pieces per box to 0. The calculator then gives only the tile count and leaves out the boxes and the cost, rather than pricing every tile as a box.
