Tile Calculator
Tiles come in whole units and you cannot un-cut a mistake, so the sum has two parts: area to cover ÷ area of one tile, then add a waste allowance (10% for a straight layout, 15% for diagonal) and round up. The calculator does both; here is what the numbers mean.
Worked example
A 4 m × 3 m floor is 12 m². With 300 × 300 mm tiles (0.09 m² each): 12 ÷ 0.09 = 133.3, round up to 134 tiles. Add 10% waste: 134 × 1.1 = 147.4, so buy 148. Tiles are often sold by the box – check the box coverage and round up to whole boxes.
Why the waste allowance is not optional
- Edge and corner cuts leave offcuts you cannot use elsewhere.
- Tiles chip during cutting and handling – budget 5-10% for breakage.
- Keep spares: matching the dye lot later is often impossible.
- Diagonal and herringbone layouts generate more offcuts – use 15%.
For scale, a UK brick face is about 215 × 65 mm, so a “brick-effect” tile is roughly that size.
Walls, floors and adhesive
The same formula covers walls – enter the wall length and height, and subtract door and window areas first. Adhesive and grout scale with area and tile size (smaller tiles mean more grout lines); the bag will state its coverage. To convert an imperial room plan, use feet to metres first, and for paint on the same job the paint calculator follows the same method.
FAQ
How many 30x30 cm tiles do I need for a 4x3 m floor?
The floor is 12 m² and each tile is 0.09 m², so 134 tiles bare. With 10% waste, buy 148.
Why do I need a waste allowance?
Cutting to fit edges and corners creates unusable offcuts, some tiles break, and you want spares for future repairs since dye lots change. 10% is standard, 15% for diagonal layouts.
How do I calculate tiles for a wall?
Same formula - use the wall length and height for the area, and subtract any door or window openings first.
Should I round up to whole boxes?
Yes. Tiles are sold by the box, and having a spare box is cheaper than a second trip and a possible dye-lot mismatch.