How it is calculated
Tiles = area ÷ (tile length × tile width) × (1 + waste)Waste (cuts and breakage) is usually 10% for straight laying and 15% for diagonal patterns or irregular rooms. Tiles are typically sold by the box or square metre.
Worked example
A 5 × 4 m floor (20 m²) with 60 × 60 cm tiles (0.36 m²): 20 ÷ 0.36 = 55.6 tiles + 10% = 62 tiles, i.e. 16 boxes of 4.
Frequently asked questions
How many extra should I buy?
About 10%, and keep a few spares for repairs since batches vary in shade.
Do grout joints matter?
Barely for normal rooms; the waste margin covers it.
How do I do a wall?
Enter the wall’s width and height and subtract door and window areas.