Calculators / Tile
By the box
Tile calculator
Enter the area and the tile size and get the count, with a waste allowance that reflects how you are laying them and boxes rounded up.
Sizes and allowances
| Option | Figure | Notes |
|---|---|---|
| Straight or grid layout | 10% | The baseline. Covers edge cuts and the occasional breakage. |
| Diagonal layout | 15% | Every perimeter tile is a cut, and each cut wastes more of the tile. |
| Herringbone or chevron | 15–20% | The most wasteful common pattern. Do not skimp here. |
| Small or busy room | 15% | More perimeter relative to area means more cuts per square foot. |
| Large-format tile | 15% | Fewer tiles, but each mistake costs more of the total. |
Waste is not optional
The waste allowance is not padding — it is the material that ends up in the offcut pile. Every tile along a wall gets cut, and the remainder of that tile is usually unusable unless the room happens to work out.
Ten percent is the floor for a simple grid in a square room. Fifteen for diagonals and small rooms, twenty for herringbone. If your calculation lands close to a box boundary, round up rather than down.
Boxes, not tiles
Tile is sold by the box, and boxes hold different counts depending on tile size. The box count is what you take to the till, so enter the tiles-per-box figure from the shelf label and let the calculator round up.
Some retailers price by square foot but still ship whole boxes. The coverage printed on the box is a useful cross-check against your own area measurement.
Batch numbers matter
Ceramic and porcelain tile is produced in runs, and colour shifts slightly between them. Boxes from a single batch will match; boxes bought two weeks later may not. Check the batch or shade code on every box before you leave, and buy the spares now.
Keep a few tiles after the job. Replacing one cracked tile from your own stock is a morning's work. Finding a match for a discontinued line is not.
Common questions
How much extra tile should I buy?
Ten percent for a straight layout in a simple room, fifteen for diagonal patterns or rooms with lots of edges, and up to twenty for herringbone.
How do I calculate tiles per square foot?
Multiply the tile width and height in inches, then divide by 144. A 12 by 24 inch tile covers 2 square feet, so 100 square feet needs 50 tiles before waste.
Should I include the grout gap?
For small tiles with wide joints, yes — it reduces the count slightly. For standard 1/8 inch joints on large tiles the effect is under one percent and the waste allowance absorbs it.
Do I need tiles from the same batch?
Yes. Shade varies between production runs, so check the batch code on every box and buy the full job, including spares, at the same time.
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