How to Calculate How Many Tiles You Need for a Floor or Wall
Tiling is unforgiving of short orders. Tiles come in production batches that can differ slightly in shade and size, and a discontinued range cannot be replaced. It pays to count carefully once and buy everything together.
There are two standard ways to count tiles. The area method is quick and gives a lower bound. The row-and-column method shows what a real layout needs, because cut tiles that cannot be reused still count as whole tiles. This article uses both on the same bathroom so you can compare them.
The area method
Find the area to cover, find the area of one tile, and divide. Use the same unit for both.
tiles = surface area ÷ area of one tile
Worked example: a bathroom floor measures 3.2 m by 2.4 m, which is 7.68 m². Each tile is 300 mm by 600 mm, or 0.3 × 0.6 = 0.18 m². Then 7.68 ÷ 0.18 = 42.67, so at least 43 tiles are needed before any waste.
For a wall, multiply the width by the height and subtract windows, doors and any niche. A splashback 2.4 m wide and 1.2 m high is 2.88 m². With square 150 mm tiles (0.0225 m² each), that is 2.88 ÷ 0.0225 = 128 tiles. Both methods agree here, because the wall divides exactly into 16 columns and 8 rows (16 × 8 = 128) with no cuts at all. Real walls rarely work out that neatly. The tile calculator does this and applies a waste percentage for you, and the area calculator helps with unusual shapes.
Allowing for grout joints
Each tile effectively occupies its own size plus one grout joint on each side. So add the joint width to both tile dimensions before finding the area of one tile.
With 3 mm joints, a 300 × 600 mm tile occupies 303 × 603 mm, or 0.1827 m². The count becomes 7.68 ÷ 0.1827 = 42.03, a little lower than before. With narrow joints the effect is small. With wide joints, or with small mosaic tiles where joints make up a large share of the surface, it matters more.
Check the spacing the manufacturer recommends, especially for rectified or large-format tiles, and use the same joint width when you calculate.
The row-and-column method
Lay the tiles out in your head, row by row. Divide each side of the room by the tile dimension along that side, and round each answer up, because a partial tile still means one tile.
Put the 600 mm side of the tile along the 3.2 m wall: 3.2 ÷ 0.6 = 5.33, which rounds up to 6 tiles per row. Across the 2.4 m wall, the 300 mm side gives 2.4 ÷ 0.3 = 8 rows. The count is 6 × 8 = 48 tiles. Adding 3 mm joints leaves the result unchanged: 3.2 ÷ 0.603 = 5.31 (6) and 2.4 ÷ 0.303 = 7.92 (8).
The count depends on which way the tile is turned. Put the 300 mm side along the 3.2 m wall instead: 3.2 ÷ 0.3 = 10.67, which rounds up to 11 tiles per row, and the 600 mm side across the 2.4 m wall gives 2.4 ÷ 0.6 = 4 rows. The count is 11 × 4 = 44 tiles, and still 44 with 3 mm joints (3.2 ÷ 0.303 = 10.56 rounds up to 11, and 2.4 ÷ 0.603 = 3.98 rounds up to 4). Work out both orientations and use the lower count as your starting point before adding waste.
The difference between the area figure of 43 and the row counts of 44 and 48 is the offcut that does not fit anywhere else. In a real layout some cut-offs can be reused on the other side of the room, so the true need for a given orientation lies between the area figure and its row count, which is why the row count is a safer starting point when you are unsure.
Waste and boxes
Even after counting rows, you need spare tiles for breakages, awkward cuts and later repairs. A 10% allowance is a common planning figure for a straightforward layout, and diagonal layouts, patterns or very large tiles may call for more. These are rules of thumb, not guarantees.
Continuing the example: 7.68 m² plus 10% is 8.448 m². If a box of tiles holds 6 tiles covering 1.08 m², you need 8.448 ÷ 1.08 = 7.82, so buy 8 boxes. That is 48 tiles covering 8.64 m², which matches the first orientation's row count of 48.
- Buy all your tiles together and check that the batch (lot) numbers match.
- Keep a few tiles unopened for future repairs.
- Shop for adhesive and grout using the maker's coverage per bag, which depends on tile size, trowel notch and joint width.
- Open several boxes and mix tiles during laying to blend slight shade differences.
If you also need the wall or floor area in other units, the area unit converter saves hand conversions. For a broader view of extra material, see our guide to waste allowances.
- Tile Calculator: Enter the size of the area, the size of one tile, the gap between tiles and a waste allowance to get the number of tiles to order. Add a box size and price to see boxes and cost.
- Area Calculator: Choose a shape, enter the measurements you know and get its area in the unit you prefer. Triangles can be solved from sides, angles, or a hypotenuse and a leg.
- Area Converter: Pick a unit on each side, type an area and the converted value appears straight away. The guide lists the exact size of every unit in square meters, with worked examples and the mistakes to avoid.
This article is general information, not professional advice. See our Disclaimer and Editorial Policy.
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