How the Tile Calculator Works
Before you tile a floor, a wall or a bathroom, you need to know how many tiles to buy. If you buy too few, you may not find the same batch again, and the color can be slightly different. If you buy too many, you spend money you did not need to. The Tile Calculator works out the number of tiles from the size of the room and of the tile, and adds an allowance for cuts and breakage.
What you enter
- The room: its length and width, or its area if you already know it, in feet or in meters.
- The tile: the width and the length of one tile, in inches or in centimeters.
- The grout joint (optional): the gap between the tiles. Each tile takes up a little more room than its own size, so a joint means you need slightly fewer tiles.
- The waste allowance: extra tiles for cuts, mistakes and breakage. The usual figure is 10%.
- Tiles in a box (optional): to round up to whole boxes.
- The price of one tile (optional): to work out the cost.
How the results are worked out
area of one tile = (tile width + joint) x (tile length + joint) tiles for the area = room area / area of one tile tiles to buy = tiles for the area x (1 + waste %), rounded up boxes = tiles to buy / tiles in a box, rounded up
A tile that is 12 inches by 12 inches is 144 square inches, or exactly 1 square foot. This is why 12 x 12 tiles are easy: one tile for each square foot of floor.
A worked example
The room is 150 square feet, and the tiles are 12 x 12 inches. The waste allowance is 10%.
| Step | Result |
|---|---|
| Area of one tile (12 x 12 / 144) | 1 sq ft |
| Tiles for the area (150 / 1) | 150 tiles |
| Waste (10% of 150) | 15 tiles |
| Tiles to buy | 165 tiles |
████████████████████████████████████████ 165 tiles ■ For the area 150 ■ For waste 15
Rounding, done right
The result must always be a whole number, and it is rounded up, since you cannot buy part of a tile. A common trap is that computers store some decimal numbers a tiny bit too high. For example, 100 x 1.1 is stored as 110.00000000000001, and rounding that up gives 111, which is one tile too many. The calculator ignores this tiny error, so 100 square feet of 12 x 12 tiles gives 110 tiles, as it should.
The size of the tile matters
The smaller the tile, the more you need. For 100 square feet, without and with 10% waste:
| Tile size | Tiles for 100 sq ft | With 10% waste |
|---|---|---|
| 4 x 4 in | 900 | 990 |
| 3 x 6 in (subway) | 800 | 880 |
| 6 x 6 in | 400 | 440 |
| 8 x 8 in | 225 | 248 |
| 12 x 12 in | 100 | 110 |
| 12 x 24 in | 50 | 55 |
| 24 x 24 in | 25 | 28 |
4 x 4 in ████████████████████████████████████████ 900 3 x 6 in ████████████████████████████████████ 800 6 x 6 in ██████████████████ 400 8 x 8 in ██████████ 225 12 x 12 in ████ 100 12 x 24 in ██ 50 24 x 24 in █ 25
The grout joint
Between the tiles there is a joint that is filled with grout. It makes each tile "bigger" by the width of the joint, so a tile and its joint cover a little more floor. For 150 square feet of 12 x 12 inch tile, with 10% waste:
| Joint | Tiles for the area | With 10% waste |
|---|---|---|
| None | 150 | 165 |
| 1/8 inch (0.125) | 147 | 162 |
| 1/4 inch (0.25) | 144 | 159 |
The joint saves you a few tiles, and the difference is larger with small tiles, as they have more joints. If you are not sure, leave it at 0 for a safe amount.
How much waste?
Tiles are cut at the walls, at corners and around pipes, and some break. The more complicated the layout, the more waste there is. For 150 square feet of 12 x 12 inch tile:
| Waste allowance | Tiles to buy | When to use it |
|---|---|---|
| 5% | 158 | A simple square room, with an experienced tiler |
| 10% | 165 | A normal room |
| 15% | 173 | Many corners, or a first-time tiler |
| 20% | 180 | Diagonal or herringbone layouts |
- Waste allowance: 5%
Tiles to buy: 158
When to use it: A simple square room, with an experienced tiler - Waste allowance: 10%
Tiles to buy: 165
When to use it: A normal room - Waste allowance: 15%
Tiles to buy: 173
When to use it: Many corners, or a first-time tiler - Waste allowance: 20%
Tiles to buy: 180
When to use it: Diagonal or herringbone layouts
5% ███████████████████████████████████ 158 10% █████████████████████████████████████ 165 15% ██████████████████████████████████████ 173 20% ████████████████████████████████████████ 180
Boxes and cost
Tiles are sold by the box. Suppose the room is 12.5 feet by 9.25 feet, which is 115.63 square feet. The tiles are 12 x 24 inches with a 1/8 inch joint, there are 8 tiles in a box, and each tile costs $3.50. The waste is 15%.
| Step | Result |
|---|---|
| Area of one tile with its joint (12.125 x 24.125) | 292.52 sq in = 2.0314 sq ft |
| Tiles for the area (115.63 / 2.0314) | 56.92, which is 57 |
| With 15% waste | 66 tiles |
| Boxes (66 / 8, rounded up) | 9 boxes, which is 72 tiles |
| Cost (72 x $3.50) | $252.00 |
You end up with 72 tiles, six more than you need. Keep these spare tiles for repairs in the future, because it may be hard to find the same tiles later.
Metric example
A room of 4 m by 3 m is 12 square meters. The tiles are 60 x 60 cm with a 3 mm joint (0.3 cm), and the waste is 10%. One tile with its joint is 60.3 x 60.3 cm, which is 0.3636 square meters. So 12 / 0.3636 gives 33.002, which is 34 tiles when rounded up, and 37 tiles with the waste.
Counting row by row
When you enter the length and width of the room, the calculator also counts the tiles row by row, where every tile that must be cut counts as a whole tile. For a room of 12.5 by 9.25 feet with 12 x 12 inch tiles, there are 12 whole tiles in a row plus a cut tile, so 13, and 9 rows plus a cut row, so 10. That makes 130 tiles, while the area gives 116. The difference shows how many tiles are lost in cuts. The drawing shows the whole tiles in green and the tiles that need to be cut in amber. If you use the offcuts in other places, you will use fewer tiles than the row count.
Tips
- Measure the room twice, and measure at the widest points. Rooms are often not square.
- Subtract areas that are not tiled, such as a bath, and add areas that are, such as a niche or a step.
- Buy all the tiles at once. Different batches can have different shades.
- Check the tile size on the box. The real size is often a little different from the name, for example 11.8 inches for a "12 inch" tile.
- Ask your tiler. They know how much waste your layout will need.
What this calculator does not include
- Grout, adhesive, underlay and trim. These are worked out from the area or the length of the edges.
- Walls with windows and doors. Subtract them from the area.
- The exact cutting plan for your room and layout.
- Tiles that are not rectangular, such as hexagons.
This tool gives an estimate for general information only. Check the amounts with your tiler or supplier before you buy.