How the tile calculator works
The calculator divides your area by the size of one tile including its grout joint, then adds an allowance for cuts and breakages based on your laying pattern. If you enter the number of tiles per box, it rounds up to whole boxes.
Tile sizes (L, W), depth and joint are in millimetres. 1.6 is the typical density of cement-based grout.
Tiles per m² for common sizes
| Tile size | Tiles per m² (3mm joint) | Typical use |
|---|---|---|
| 100 × 100mm | 94.3 | Splashbacks, feature walls |
| 300 × 300mm | 10.9 | Floors, walls |
| 600 × 300mm | 5.5 | Bathroom walls & floors |
| 600 × 600mm | 2.75 | Kitchen & living floors |
| 1200 × 600mm | 1.38 | Large-format floors & walls |
Tiling tips
- Prime the surface first. Plasterboard, plywood and anhydrite screed each need the correct primer for your adhesive.
- Use a flexible (S1) adhesive on timber floors, underfloor heating and large-format porcelain.
- Back-butter large tiles and aim for at least 90% adhesive coverage on floors (100% in wet areas and outdoors).
- Start from the centre of the room, or from a visible line, so cuts at the edges are even and no smaller than half a tile.
- Check that all boxes have the same batch or shade number before you start.
Worked examples
A 3m × 2.5m kitchen floor in 600 × 600mm porcelain: 7.5m² plus 10% = 8.25m². Each tile with a 3mm joint covers 0.364m², so you need 23 tiles. At a 10mm trowel notch the adhesive is about 31.5kg (2 × 20kg bags). The grout is only about 1.3kg, because big tiles have very few joints. Large tiles need a flat floor: check it with a long straight edge before you start.
A 2.4m × 2m bathroom wall in 300 × 75mm metro tiles: 4.8m² plus 10% needs about 224 tiles, around 4kg of grout. That's three times as much grout per m² as the floor, simply because there are so many more joints. Pick "Custom size" for tiles not in the list.
Wet areas need more than tiles
Tiles and grout aren't waterproof on their own. In showers and wet rooms, the wall and floor behind the tiles must be tanked with a waterproofing membrane or kit, especially at corners, joints and round the tray. Use moisture-resistant plasterboard or cement-based backer board rather than standard plasterboard. The UK code of practice for tiling (BS 5385) sets out the details, and adhesive makers publish compatible systems. Use their primer, membrane and adhesive together.
Preparing the surface
- Floors: must be firm, flat and not flex. Overboard timber floors with 15mm or thicker plywood or tile backer board, and level dips with self-levelling compound.
- Walls: plaster and plasterboard need priming. Painted walls should be sound and keyed. Don't tile onto wallpaper or flaking paint.
- Weight: heavy stone and large porcelain tiles have weight limits on plastered walls. Check the tile maker's guidance.
Common tiling mistakes
- Starting in a corner. Walls are rarely straight, and you'll end up with thin slivers on the far side. Set out from a central line instead.
- Dot-and-dab adhesive on floors. Hollow spots under tiles crack when weight goes on them. Use a full bed with a notched trowel.
- Grouting too soon. Let the adhesive set for the time on the bag before grouting, usually 24 hours for standard adhesives.
Tiling a kitchen splashback? Measure the area above the worktop. The worktop calculator covers the worktops. For a floating floor instead, see the flooring calculator.