Tile Calculator

2026-10-17

Find out how many tiles, boxes and how much grout you need for a floor or wall. Add several rectangles for L-shaped rooms, subtract cut-outs, choose a layout pattern and waste allowance, and see the cost and a to-scale preview. Metric or imperial.

How to use the tile calculator

1. Pick metric or imperial. Switching converts the lengths you have already typed; prices are left as they are.
2. Enter the length and width of the area to tile. For an L-shaped room, press “Add rectangle” and split the room into rectangles. Use Add for extra sections and Subtract for parts you will not tile, such as a bathtub or a kitchen island.
3. Enter the tile length and width and the grout joint. Use 0 for tiles laid with no visible gap.
4. Choose the layout pattern. The waste allowance fills in a suggested value that you can overwrite.
5. Optionally enter the contents of one box, a price and the tile thickness for a grout estimate. Leave a field empty to skip that line.
6. Read the number of tiles, boxes, cost and grout, and check the preview. “Copy results” puts a plain-text summary on the clipboard.

How it works

The calculator first finds the net area A: the sum of the rectangles you add minus the rectangles you subtract. Each rectangle is length × width.

A tile never sits alone: it takes up its own face plus one grout joint. With tile length L, tile width W and joint width j, one tile covers a cell of (L + j) × (W + j). The number of tiles is:

tiles = A / ((L + j) × (W + j))

All lengths are converted to the same unit first. The exact figure is usually a fraction, so it is rounded up. The waste allowance w (in percent) is applied to the exact figure and the result is rounded up again:

tiles to buy = ceil(tiles × (1 + w / 100))

Boxes: if a box holds n tiles, boxes = ceil(tiles to buy / n). If the box is given as a covered area, the calculator divides that area by the face area of one tile (L × W) to get n. The cost is calculated on whole boxes, because that is what you pay for. If you give no box size, it uses the tiles to buy instead.

Grout: the joints form a thin grid, so the volume per unit of area is T × j × (L + W) / (L × W), where T is the tile thickness. Multiplied by the area, then by an assumed density of 1,600 kg per cubic metre for mixed cement grout, and increased by 10 % for waste and uneven joints, this gives the amount shown. It is an approximation: joint depth, tile edges and the product all change the real figure.

Examples

Example 1 — the default room. A 4 m × 3 m floor, 30 × 30 cm tiles, 3 mm joints, straight layout, 10 % waste. Area 12.00 m². One cell is 0.303 × 0.303 = 0.091809 m², so 12 / 0.091809 = 130.7 tiles, which is 131 when rounded up. With waste: 130.7 × 1.10 = 143.8, so 144 tiles. At 11 tiles per box that is 14 boxes (154 tiles); at 1.80 per tile the cost is 154 × 1.80 = 277.20. With 8 mm thick tiles the grout is about 3.4 kg.

Example 2 — a small bathroom. 2.4 m × 1.8 m = 4.32 m², the same tiles and joints, 10 % waste. Exact: 47.1 tiles, so 48 without waste and 52 tiles with it. With 10 tiles per box you buy 6 boxes (60 tiles). Priced at 32 per m², you pay for 6 × 0.9 m² = 5.4 m², which is 172.80.

Example 3 — an L-shaped room. Add a 5 m × 4 m rectangle and subtract a 2 m × 1.5 m notch: 20 − 3 = 17.00 m². Tiles are 60 × 30 cm with 2 mm joints, laid in a brick pattern with 12 % waste. A cell is 0.602 × 0.302 = 0.181804 m², giving 93.5 tiles exactly (94 rounded up) and 105 tiles with waste. A box covers 1.44 m², which is 8 tiles, so you need 14 boxes. At 45 per box the cost is 630.00.

Example 4 — imperial, diagonal. A 12 ft × 10 ft room is 120.00 ft² (11.15 m²). Tiles are 12 × 12 in with a 0.125 in joint, so a cell is 12.125 × 12.125 = 147.02 in². Exact count: 117.5 (118 rounded up). A diagonal layout with 15 % waste gives 136 tiles. A box covers 12 ft² (12 tiles), so you need 12 boxes (144 tiles). At 3.20 per ft² the cost is 144 × 3.20 = 460.80.

Choosing a layout and a waste allowance

The suggested allowances are common rules of thumb, not laws. A straight grid needs the fewest cuts: only the last tile in each row and column is trimmed, and the offcut of one row can often be used at the start of the next. About 10 % is typical. A brick or offset pattern shifts every second row by half a tile, which adds cuts at both ends of the rows, so 10 to 12 % is usual. A diagonal layout cuts almost every tile along the walls into triangles, and 15 % is a common figure.

Raise the allowance for large-format tiles and rooms with many corners or pipes. Whatever you choose, keep a few spare tiles from the same batch: shade and size vary between production runs.

Common mistakes

• Mixing units. Tiles are often sold in centimetres or inches while rooms are measured in metres or feet. The calculator converts for you, but check each label.
• Ignoring the joint. Leaving out the grout gap makes the count too low, most noticeably with small tiles and wide joints.
• Rounding down. Part of a tile cannot be bought, and a partial box does not exist. Always round up.
• Forgetting walls and openings. For a wall, enter its length and height as a rectangle and subtract windows and doors.

Frequently asked questions

How much extra tile should I buy?

Ten percent is the usual minimum for a straight layout. Use 12 % for brick patterns and 15 % for diagonal ones, and more for complicated rooms. You can type any value from 0 to 100.

Can I use it for walls?

Yes. Treat each wall as a rectangle (length × height), add them, and subtract windows, doors and any area that will stay untiled.

What grout joint width should I enter?

Rectified tiles with precise edges are often laid with joints of about 2 to 3 mm (1/16 to 1/8 inch). Rougher or handmade tiles need wider joints.

How accurate is the grout estimate?

It is only approximate. It assumes full, flat joints and a fixed density, plus a 10 % margin. The coverage table on the grout packaging is more reliable for the specific product.

Why is the cost higher than tiles times price?

When you enter a box size, the cost covers whole boxes, including the tiles left over after the last one is opened. Without a box size the cost uses the tiles to buy.

Is my data stored or uploaded?

No. All calculations run in your browser. Your entries are kept only in your browser's local storage so they are still there when you return, and nothing is sent to a server.

Related tools

• Unit Converter — convert between metres, feet, inches and other units.
• Percentage Calculator — work out waste, discounts and price changes.
• Loan Calculator — plan the monthly payments for a larger renovation.
• Paint Calculator — estimate paint for the same room.