How many tiles do I need?
Tiles = room area × (1 + wastage) ÷ area of one tile
Boxes = tiles ÷ tiles per box, rounded up
Boxes = tiles ÷ tiles per box, rounded up
A 600 × 600 mm tile covers 0.36 m², so a 6 × 4.5 m room of 27 m² with 10% wastage needs 29.7 ÷ 0.36 = 83 tiles. At 4 tiles per box, order 21 boxes.
Grout quantity formula
Tile manufacturers use this formula for grout consumption:
Grout (kg/m²) = (A + B) ÷ (A × B) × C × D × 1.6
A, B = tile length and width (mm) · C = joint width (mm) · D = joint depth (mm)
A, B = tile length and width (mm) · C = joint width (mm) · D = joint depth (mm)
Larger tiles have fewer joints per square metre, so they use much less grout.
Adhesive coverage guide
| Tile size | Trowel notch | Typical adhesive |
|---|---|---|
| Up to 300 × 300 mm | 6 mm | 3–4 kg/m² |
| 600 × 600 mm | 10 mm | 4–6 kg/m² |
| Large format, 800 mm and above | 12 mm + back-buttering | 6–8 kg/m² |
Check the adhesive bag for the manufacturer's coverage, which varies by product.
Frequently asked questions
How much extra tile should I order?
10% for straight layouts, 15% for diagonal and patterned layouts, and keep a few spare tiles from the same batch for future repairs.
Should I deduct fixed furniture?
Only deduct areas that will never be tiled, such as under built-in kitchen units if they sit on a plinth. Otherwise tile the full floor.