Tile Calculator
Enter the length and width of the area, the size of one tile, the grout joint between tiles and a waste allowance for cuts. The calculator counts the tiles that fit, adds your allowance, and rounds up to whole tiles and whole boxes.
Answer
You need
87tiles
9 boxes of 10 — 90 tiles, 3 spare.
- sq ft to tile
- 80
- tiles before waste
- 78.36
- boxes of 10
- 9
- spare tiles
- 3
Check the work
Every line comes from the same calculation as the answer.
tiles = ⌈ area ÷ ((tile + joint) × (tile + joint)) × (1 + waste) ⌉
| area | 10 × 8 | 80 sq ft |
|---|---|---|
| tile + joint | (12 ÷ 12) + (0.125 ÷ 12) | 1.010417 ft |
| per tile | 1.010417 × 1.010417 | 1.020942 sq ft |
| tiles | 80 ÷ 1.020942 | 78.359 |
| with waste | ⌈ 78.359 × (1 + 0.1) ⌉ | 87 |
| boxes | ⌈ 87 ÷ 10 ⌉ | 9 |
How it works
A tile covers a little more ground than its own face, because every tile sits inside a grout joint. A 12-inch tile laid with 1/8-inch joints takes up a square of 12 1/8 inches, so the count is the surface area divided by that larger square, not by the tile alone.
Tile sizes are usually given in inches or centimetres while rooms are measured in feet or metres. The calculator converts the tile and the joint into the room’s unit before dividing, and shows that conversion in the working so nothing happens out of sight.
Cuts at the edges, around a toilet or along a doorway use up whole tiles, and some break. That is what the waste allowance is for. Straight layouts in simple rooms commonly need less than diagonal or herringbone layouts; the figure you enter is your own planning choice.
Formula
tiles = ⌈ length × width ÷ ((tile length + joint) × (tile width + joint)) × (1 + waste) ⌉
The area is divided by the space one tile occupies including its joint, the waste allowance is added, and the result is rounded up to whole tiles and then to whole boxes.
Worked examples
- Try these numbers
Kitchen floor, 12-inch tiles with 1/8-inch joints
- The floor is 10 × 8 = 80 sq ft.
- Each tile occupies 12.125 in square, which is 1.0104 ft; 1.0104 × 1.0104 = 1.0209 sq ft.
- 80 ÷ 1.0209 = 78.36 tiles; adding 10% gives 86.19, which rounds up to 87 tiles.
- 87 tiles at 10 per box is 8.7, so 9 boxes.
Buy 9 boxes (90 tiles); 3 are spare.
- Try these numbers
Bathroom floor in metres, 30 cm tiles with 3 mm joints
- The floor is 4 × 3 = 12 m².
- Each tile occupies 0.303 m square: 0.303 × 0.303 = 0.0918 m².
- 12 ÷ 0.0918 = 130.71 tiles; with 10% waste, 143.78 rounds up to 144.
- 144 ÷ 11 = 13.09, so 14 boxes.
Buy 14 boxes (154 tiles); 10 are spare.
- Try these numbers
Small panel that tiles exactly
- A 2 × 2 m panel is 4 m².
- Butt-jointed 50 cm tiles cover 0.25 m² each: 4 ÷ 0.25 = 16 tiles.
- 16 tiles at 4 per box is exactly 4 boxes.
Buy 4 boxes with none spare — add a waste allowance if any tile has to be cut.
Inputs and results
- Area length
- One side of the tiled rectangle, in feet or metres.
- Area width
- The other side, in the same unit.
- Tile length
- One side of a tile, in inches or centimetres.
- Tile width
- The other side of a tile, in the same small unit.
- Joint width
- The grout gap between tiles, in inches or millimetres. Enter 0 for butt-jointed tiles.
- Waste allowance
- Extra tiles for cuts and breakage, as a percentage you choose.
- Tiles per box
- How many tiles one box contains, from the box label.
- Tiles to cover the area
- Surface area divided by the area of one tile plus its joint.
- Tiles including waste
- The covering count with your waste allowance added, rounded up to whole tiles.
- Boxes
- Tiles to buy divided by tiles per box, rounded up.
- Spare tiles
- Tiles left in the last box beyond those you planned to use.
When to use it
- Ordering floor tiles for a bathroom or kitchen and wanting the number of boxes, not just the area.
- Seeing how much a wider grout joint or a larger tile changes the number of tiles needed.
- Planning a splashback or shower wall, measured as a rectangle of tiled surface.
Common mistakes
- Entering the tile size in feet or metres after choosing inches or centimetres; the tile field is in the small unit shown beside it.
- Leaving the joint out. A few millimetres per tile adds up across a floor and reduces the count, which is why tile packs quote coverage with joints.
- Forgetting that a box is sold whole: 87 tiles at 10 per box is 9 boxes, with 3 tiles spare.
What it does not do
- It handles one rectangle at a time; split an L-shaped room into rectangles and add the results.
- It does not plan a layout or tell you where cuts fall, so it cannot say how many cut pieces can be reused.
- It does not estimate adhesive, grout, trim or backer board.
Method and assumptions
Tile and joint sizes are converted to the area unit (12 inches to the foot, 100 centimetres and 1,000 millimetres to the metre). The surface area is divided by the area each tile occupies including one joint width in each direction.
The waste allowance multiplies the covering count, which is then rounded up to whole tiles, and tiles are rounded up again to whole boxes. A tiny floating-point remainder is removed before rounding so an exact count is not pushed up by one.
Assumptions
- The tiled area is a rectangle.
- Each tile takes up its own size plus one joint width in each direction.
- Boxes are bought whole.
Edge cases
- A joint of 0 treats tiles as butted together.
- Tiles per box must be a whole number of at least 1.
- A tile larger than the whole area still counts as one tile; check that such a layout makes sense.
Sources and corrections
This calculator uses an elementary formula, so it needs no outside data source. The method, the rounding rules and how a reported error is corrected are set out in the site standards.
Result looks wrong?
Send the inputs you used and the answer you expected. Every report is checked against the formula and its tests, and confirmed errors are corrected in public.