How to use the Tile Calculator (Tiles and Boxes Needed)
- Enter the length and width of the area to tile, in metres.
- Enter the tile length and width in centimetres, and the grout gap in millimetres.
- Enter the waste allowance and the number of tiles in a box.
- Read the tiles and boxes to buy.
Formula used
Tile footprint = (tile length + gap) × (tile width + gap). Tiles = area ÷ footprint, plus the waste percentage, rounded up. Boxes = tiles ÷ tiles per box, rounded up.
Worked example
Here is the Tile Calculator (Tiles and Boxes Needed) worked through with the example values shown above, so you can check each step by hand.
| Inputs | |
|---|---|
| Area length (m) | 4 |
| Area width (m) | 3 |
| Tile length (cm) | 60 |
| Tile width (cm) | 60 |
| Grout gap (mm) | 3 |
| Allowance for cuts and waste | 10 % |
| Tiles per box | 4 |
| Result | |
| Tiles to buy | 37 |
| Boxes to buy | 10 |
| Area to tile (m²) | 12 |
| Tiles needed with no waste | 34 |
How the count is made
A 4 m by 3 m floor has an area of 12 m². Each 60 cm by 60 cm tile with a 3 mm grout gap takes up 60.3 cm by 60.3 cm. That means 34 tiles are needed with no waste. With a 10% allowance, buy 37 tiles.
If the tiles come in boxes of 4, that is 10 boxes. Always round up to whole boxes, since partial boxes cannot be bought.
How much to allow for waste
Cut tiles at the edges, breakages and rejects all mean you use more than the floor area alone. About 10% suits simple straight layouts. A diagonal layout, a small or irregular room or a patterned tile calls for 15% or more. At 15% the example needs 38 tiles.
It helps to keep a few spare tiles after the job for future repairs, as the same batch may not be available later.
Gaps and tile size
Grout lines make each tile cover slightly more than its own size. Ignoring a 3 mm gap would give 34 tiles in the example instead of 34, a small difference on a large tile but a larger one on mosaic or small tiles.
Smaller tiles mean more cuts. 30 cm tiles in boxes of 11 for the same floor need 144 tiles (14 boxes) including the allowance.
Walls and awkward spaces
For a wall, enter its length and height as the area length and width. For an L-shaped room, split it into rectangles, run the calculator for each and add the results, remembering to add waste to each part. Subtract doors, windows or a bath panel from the wall area by running it for those too and taking the difference.
The calculator assumes a simple grid. Features like pipes and corners add cuts, so check with your tiler for tricky layouts.
Frequently asked questions
How many tiles should I buy extra?
About 10% is usual, and 15% or more for diagonal patterns or small rooms.
Do I need to include the grout?
Yes, enter the gap width so tile size includes the grout line.
What units does it use?
Area in metres, tiles in centimetres and the gap in millimetres.
Does it give the weight or adhesive needed?
No. Adhesive coverage is printed on the bag, and you can use the area result with it.
Can I use it for wall tiles?
Yes, enter the wall’s length and height.
Why are boxes rounded up?
Tiles are sold in whole boxes.
This calculator gives estimates for information only. Actual figures from a bank, employer, tax authority or doctor may differ. It is not financial, tax, legal or medical advice.