How to calculate how many tiles you need
- Measure the area. Multiply length by width. For odd shapes, split into rectangles and add them up.
- Work out the area of one tile, adding the grout joint to each side: a 12 × 12 in tile with a 1/8 in joint covers 12.125 × 12.125 in.
- Divide the room area by the tile area and round up.
- Add waste for cuts and breakage, then round up to whole boxes.
How much waste should I add?
| Layout | Extra tiles |
|---|---|
| Straight lay, large rectangular room | 5–10% |
| Standard room with a few obstacles | 10% |
| Diagonal, herringbone or small room with many cuts | 15% |
| Complex shapes, large-format tiles | 15–20% |
Tiles per square foot and per square metre
| Tile size | Tiles per sq ft | Tiles per m² |
|---|---|---|
| 4 × 4 in (10 × 10 cm) | 9 | 100 |
| 6 × 6 in (15 × 15 cm) | 4 | 44.4 |
| 12 × 12 in (30 × 30 cm) | 1 | 11.1 |
| 12 × 24 in (30 × 60 cm) | 0.5 | 5.6 |
| 24 × 24 in (60 × 60 cm) | 0.25 | 2.8 |
Keep a few spare tiles after the job: matching the exact colour batch later is often impossible. Measuring the room first? Use the square footage calculator; pouring a new slab underneath? See the concrete calculator.
Choosing the grout joint width
Joint width depends on the tile edge. Rectified tiles (with precisely cut edges) can be laid with joints of 2–3 mm (about 1/16–1/8 in). Pressed tiles with slightly irregular edges need wider joints, typically 3–6 mm (1/8–1/4 in), to absorb the size variation. Follow the tile manufacturer’s minimum and the TCNA Handbook for installation methods.
Tiling a wall or a backsplash
- Measure the height and width of each wall section and multiply.
- Subtract windows, doors and areas behind fixed units.
- Add the areas, then add 10–15% waste: walls have more cuts around outlets and edges.
- For a backsplash, measure only between the worktop and the wall cabinets.
What else to buy
- Adhesive (thinset): one 25 kg (50 lb) bag usually covers about 4–5 m² (45–55 sq ft) with a standard notched trowel — check the bag.
- Grout: the amount depends on tile size and joint width; small tiles with wide joints use far more.
- Spacers, levelling clips and trims for edges and corners.
Measuring an irregular room? Split it into rectangles with the square footage calculator. Preparing a new base first? The concrete calculator gives the slab volume.