How many tiles do I need?
The short answer is the floor area divided by the area of one tile, plus an allowance for cuts and breakages. The longer answer depends on three things most quick calculators ignore: the joint between tiles, the laying pattern, and the fact that tiles are sold in boxes, not one at a time.
This calculator counts each tile together with one joint, so a 600 × 600 mm tile with a 2 mm joint covers 602 × 602 mm of floor. It then adds waste based on the pattern you choose and rounds up to whole boxes, showing the area you are actually buying next to the area you need.
Waste by pattern
Every cut at a wall, door frame or pipe produces an offcut that may not be usable elsewhere. Patterns that put tiles at an angle to the walls produce more of them. The defaults are:
- Straight (grid) and offset 1/2 or 1/3 (brick bond): 10%.
- Diagonal 45°: 15%.
- Herringbone: 18%.
- Plus 5% for small rooms under 4 m², where almost every tile is cut, and 3% for large-format tiles with an edge of 1200 mm or more, which break more easily.
The tile formula
N = ⌈ A × 10⁶ ÷ ((L + j) × (W + j)) × (1 + waste) ⌉, boxes = ⌈ N ÷ pieces per box ⌉
A is the floor area in m², L and W are the tile length and width in mm, and j is the joint width in mm. The leftover is the number of tiles in the boxes you buy minus the net number of tiles the floor needs.
Worked example
- Room 4.0 × 3.0 m = 12.00 m², tile 600 × 600 mm, 2 mm joint, straight pattern, 10% waste, 4 tiles per box.
- N_net = 12 × 10⁶ ÷ (602 × 602) = 33.11 tiles.
- With 10% waste: 33.11 × 1.10 = 36.4 → 37 tiles.
- Boxes: ⌈37 ÷ 4⌉ = 10 boxes = 40 tiles = 14.40 m². Leftover: 40 − 33.1 = 6.9 tiles.
Precise count for rectangular rooms
For a rectangular room laid straight or offset, you can switch on the grid method. It counts full columns and rows and looks at the cut pieces at the edges. If a cut piece is less than half a tile and the pattern is not directional, two cuts come from one tile. A 3% breakage allowance is added, and the calculator uses whichever count — area or grid — is larger.
Boxes, pallets and a spare box
Enter the box contents as pieces per box or m² per box; the other value is derived, and you will be warned if the two do not match the tile size. If you are buying in bulk, enter boxes per pallet to see the order as pallets plus loose boxes. Many tilers keep one spare box from the same production batch for future repairs, because a later batch can differ slightly in shade — tick “keep a spare box” to add it.
Adhesive, grout and accessories
The trowel notch is suggested from the longest tile edge, and adhesive consumption follows from it. Grout is calculated from the tile size, joint width and tile thickness. Spacers are counted per tile, and from 600 mm upwards levelling clips are switched on automatically to keep large tiles flush.
Frequently asked questions
Should I include the joint width in the tile calculation?
Yes, for accuracy. With small tiles and wide joints the difference is significant: 100 × 100 mm mosaic with 3 mm joints needs about 6% fewer tiles than the area alone suggests.
How many extra tiles should I buy?
Usually 10% for a straight pattern, more for diagonal or herringbone, and more again in small rooms. Keeping one spare box for future repairs is a good idea with any tile.
How do I calculate tiles for an L-shaped room?
Choose the L/U shape mode and walk around the room, entering each wall length and whether you turn left or right at its end. The calculator computes the exact area and perimeter from the walls.
Do I subtract the bathtub or kitchen island?
Yes, if you will not tile under it. Add it as an exclusion; its area is subtracted, and you can choose whether it needs skirting around it.
Can I enter the box size in square metres?
Yes. Choose “m² per box” and the calculator derives the number of tiles per box from the tile size, warning you if the two disagree by more than 2%.