Tile calculator — how many tiles for a bathroom?
Enter the dimensions of the surface and the tile size. You get square metres including the allowance, the number of pieces and the number of boxes. It works the same for floors and walls — just enter the dimensions of the surface you are tiling.
The formula
(area × (1 + allowance) ÷ area of one tile) = number of tiles
Worked example for a 2.5 × 2 m bathroom, 60 × 60 cm tiles, 10% allowance:
- Floor: 2.5 × 2 = 5 m²
- With allowance: 5 × 1.10 = 5.5 m²
- One tile: 0.6 × 0.6 = 0.36 m²
- Pieces: 5.5 ÷ 0.36 = 15.3 → 16 tiles
- With 1.44 m² boxes: 5.5 ÷ 1.44 = 3.8 → 4 boxes
Watch the proportions in a bathroom: the same room has 5 m² of floor but, at 2.5 m high, a full 22.5 m² of wall. Calculate walls separately, subtracting the door and any window.
How much allowance to add
| Laying pattern | Allowance | Why |
|---|---|---|
| Straight, rectangular room | 10% | Standard, cuts along the walls |
| Large format, simple surface | 5–7% | Fewer cuts per m² |
| Diagonal (45°) | 15% | Every edge is a cut |
| Herringbone / offset brick | 15% | Heavy waste at row ends |
| Room with recesses and slopes | 15–20% | Irregular edges |
Easy things to forget
- One production batch. Tiles from different batches differ in shade and calibre. Buy the full quantity at once, allowance included.
- Keep a few spares. In three years the range may be gone, and a cracked tile always happens eventually.
- Adhesive and grout are a separate cost. Adhesive usage depends on tile format and trowel size — large formats can use twice as much as small ones.
- Trims and corner profiles. For wall tiles, measure the running metres of finishing profiles.
Not sure of the dimensions yet? Decoria.Studio scans the room with your phone, works out the floor and wall area itself, then builds a shopping list with quantities and prices — square metres of tiles included.
Questions and answers
How many tiles for a 5 m² bathroom?
With 60 × 60 cm tiles and a 10% allowance, 16 pieces for the floor alone. Remember that bathroom walls are usually a bigger surface than the floor — a 2.5 × 2 m bathroom has 5 m² of floor but around 22 m² of wall.
How much extra should I allow for tiles?
10% for straight laying. For diagonal or herringbone patterns, or an irregularly shaped room, allow 15%. With large formats in a simple rectangular room 5–7% is enough.
Do grout lines count in the calculation?
They do not need to. A 2–3 mm grout line slightly reduces the number of tiles, so ignoring it means you calculate with a small surplus — and that is the safer direction to be wrong in.
Do all tiles need to come from the same batch?
Yes. Tiles from different production batches can differ in shade and in calibre, meaning their actual size differs by fractions of a millimetre. The batch number is printed on the box — buy the whole quantity at once, allowance included.
Why keep spare tiles after the work is done?
To replace a cracked tile years later. The same range may be discontinued, and a new batch would differ in shade anyway. Two or three spare tiles are the cheapest insurance in any renovation.