Tile Calculator
Estimate how many tiles a job needs from the area to cover, the size of each tile, the grout gap between tiles, and a waste allowance for cuts and breakages. Enter the room as length times width or as a total area, then turn on the cost estimate to price tiles by the box. Works in metric (m², centimetres) or imperial (square feet, inches), with a sensible 10% default for offcuts.
Formula
Worked example
Metric: a 4 × 3 m floor is 12 m². With 30 × 30 cm tiles and a 3 mm grout gap, each tile effectively covers 0.303 × 0.303 = 0.0918 m², so 12 ÷ 0.0918 = 130.7, rounded up to 131 tiles bare. Add 10% waste: 130.7 × 1.10 = 143.8, rounded up to 144 tiles. At 6 tiles per box that is 24 boxes, and at 25 per box it costs about 600.
How the tile count is worked out
The estimate starts with the area you want to cover and the footprint of a single tile. You can enter the room as length times width or type a total area directly, which is handy when you have already measured an irregular space. Dividing the total area by the area of one tile gives the number of tiles needed before any cutting, and because you cannot buy a fraction of a tile the result is always rounded up to the next whole tile. The calculator keeps the tile width and height separate so it handles rectangular and plank-style tiles, not just squares, and it converts those dimensions into the same unit as the area before dividing.
Grout gaps and effective coverage
Tiles are not laid edge to edge; a small grout joint sits between them. That joint means each tile effectively claims a little more floor than its bare size, so a wider gap slightly reduces the number of tiles you need. The calculator adds the grout gap to both the width and the height of each tile to find the effective coverage, then divides the area by that figure. A typical floor joint is 2 to 5 mm (about 1/8 inch); leave the gap at zero to size by the bare tile. Because the difference is small, the waste allowance usually more than absorbs it, but accounting for the gap keeps large-format and large-gap layouts accurate.
Why a waste allowance matters
Almost no room divides neatly into whole tiles, so tiles around the edges and around fittings have to be cut, and the offcuts are usually too small to reuse. A waste allowance adds a percentage of spare tiles to cover those cuts, the occasional breakage during handling, and a handful held back for future repairs. A simple straight layout in a square room typically needs about 10%, which is the default here. Diagonal or herringbone patterns, rooms with many alcoves and pipes, or large-format tiles that crack more easily can justify 15-20%. Ordering the spares in the same batch protects you against shade variation between production lots, which is often visible even within the same product range.
Boxes and the cost estimate
Tiles are sold by the box, not individually, so the real order is rounded up to whole boxes. Turn on the cost estimate, enter how many tiles come in a box and the price of one box, and the calculator works out the boxes to buy and the total tile cost. The total is a planning figure for the tiles alone; remember to also budget for adhesive, grout, spacers, trim, and any tools, whose quantities depend on tile size, joint width, and the surface being covered. Buying complete boxes from a single batch keeps the shade consistent and leaves a few spares for future repairs.
Measuring the area accurately
For a rectangular floor, multiply the length by the width to get the area; for an L-shaped or irregular space, split it into rectangles, work out each one, add them together, and enter the total using the total-area mode. When tiling walls, measure each wall separately and subtract large openings such as windows and doorways so you are not buying tiles you will never lay. Always measure the room rather than relying on a plan, because real walls are rarely perfectly square.
Common tile sizes and coverage
| Tile size | Area per tile | Tiles per m² | Tiles per 10 m² |
|---|---|---|---|
| 10 × 10 cm | 0.01 m² | 100 | 1000 |
| 15 × 15 cm | 0.0225 m² | 44.4 | 444 |
| 20 × 20 cm | 0.04 m² | 25 | 250 |
| 30 × 30 cm | 0.09 m² | 11.1 | 111 |
| 45 × 45 cm | 0.2025 m² | 4.9 | 49 |
| 60 × 60 cm | 0.36 m² | 2.8 | 28 |
Approximate area covered by one tile, before grout joints and waste.
Frequently asked questions
How much extra should I add for waste?
Around 10% is a safe default for a straight layout in a simple, square room. Increase it to 15-20% for diagonal or herringbone patterns, rooms with lots of alcoves and pipework, or large-format tiles, which are easier to crack and produce more unusable offcuts.
Does this account for grout lines?
Yes. Enter the grout gap and the calculator adds one joint to the width and height of each tile, so each tile effectively covers a little more area and you need slightly fewer. A typical floor joint is 2 to 5 mm. Leave the gap at zero to size by the bare tile area.
How many boxes of tiles should I buy?
Turn on the cost estimate and enter the tiles per box from the product label. The calculator rounds the total tile count up to whole boxes, since tiles are sold by the box. Buying complete boxes from one batch keeps the shade consistent and leaves a few spares for future repairs.
Can I enter a total area instead of room dimensions?
Yes. Switch the area input to "Total area" and type the square metres or square feet you have already measured. This is useful for L-shaped or irregular rooms, where you split the space into rectangles, add the areas together, and enter the sum.