Tile calculator — how many tiles to buy
This calculator tells you how many tiles to order for a floor or wall, including a margin for cuts and breakages. It is built for DIY renovators and trade estimators sizing up a tiling job before buying materials.
How it works
The tool computes two areas and applies a waste factor:
surface area = surface length × surface width
tile area = tile length × tile width (converted to surface units)
base tiles = surface area ÷ tile area
tiles needed = ceil(base tiles × (1 + waste% / 100))In metric mode, surface dimensions are metres and tile dimensions centimetres (converted at 0.01 m/cm); in imperial mode, surfaces are feet and tiles inches (converted at 1/12 ft/in). The base count is multiplied by the waste factor and rounded up to whole tiles, since you can’t buy a fraction.
Example
A 4 m × 3 m floor is 12 m². With 30 cm × 30 cm tiles, each tile covers 0.30 × 0.30 = 0.09 m², so the base count is 12 ÷ 0.09 ≈ 133.3 tiles. Adding a 10% waste allowance gives 133.3 × 1.10 ≈ 146.7, rounded up to 147 tiles.
| Waste allowance | Typical use |
|---|---|
| 10% | Straight, grid layouts (default) |
| 15% | Larger tiles, some cuts |
| 20% | Diagonal patterns, complex rooms |
Choosing the right waste allowance
The waste percentage is the most variable input and the one most worth thinking about carefully before you order. Ordering too few means a second trip to the shop — where the batch may be a slightly different shade — while ordering too many leaves usable tiles on a shelf.
10% waste works well for rectangular rooms with straight grid layouts and small tiles where cuts are simple right angles. If the room is a straightforward rectangle and the tiles are 20 × 20 cm or smaller, 10% is typically sufficient.
15% waste is appropriate when you are using larger-format tiles (60 × 60 cm or above), because large tiles produce more waste per cut — a single failed cut on a 60 cm tile discards more material than a failed cut on a 20 cm tile. It is also the right choice for rooms with alcoves, built-in furniture, or irregular shapes that require many partial tiles.
20% waste applies to diagonal patterns. Laying tiles at 45 degrees to the wall increases cuts significantly because every tile along the perimeter must be cut to fit the diagonal edge. It is also prudent for materials that are fragile or expensive to source, where the cost of a second order outweighs the cost of holding extra stock.
Planning the layout before calculating
A quick layout sketch helps you estimate whether the actual waste will be toward the top or bottom of the range for your chosen percentage. Walk through the room and count the tiles that will need to be cut: tiles at the edges, around obstacles (toilet bases, islands, hearths), and at doorways. If you count more than about 10% of the total tile count as partial tiles, you are likely toward the higher end of the waste range for your layout.
For rooms where a full tile will land awkwardly — for example a 1.2-metre room tiled with 40 cm tiles would end with one 40 cm tile plus one 40 cm tile equals 80 cm, leaving a 40 cm gap at one end — it is worth adjusting the starting position so cuts are evenly split between opposite walls. That does not change the tile count, but it does change where the cut tiles land and can improve the finished appearance significantly.
Buying in the same batch
When you buy tiles, buy them all from the same production batch if possible. Ceramic tiles are manufactured in batches (sometimes labelled as a “lot” or “calibre” number on the box), and slight colour or size variations between batches are common, particularly for natural-look tiles where the variation is intentional. If you underestimate and need to return for more tiles from a different batch, the difference may be visible in the finished floor.
The safest approach is to add an extra 10% to your calculated total and hold onto unopened boxes until the floor has been grouted and inspected. Unopened tiles can usually be returned. A visible batch mismatch cannot be reversed without re-tiling the affected section.
All calculations run instantly in your browser; nothing is uploaded.