How to use this calculator
- Enter or choose units.
- Enter or choose area length.
- Enter or choose area width.
- Enter or choose tile length.
- Enter or choose tile width.
- The tiles to buy updates as you type. Use Copy result or Share to keep it.
Method
Tiles = Area ÷ ((Tile length + Joint) × (Tile width + Joint)) × (1 + Waste%), rounded up; Boxes = Tiles ÷ Tiles per box, rounded up
- Area
- length × width of the surface
- Joint
- grout joint width
- Waste%
- extra for cuts, breakages and spares
Worked example
- Area = 4 × 3 = 12 m². Each tile with a 3 mm joint takes 0.303 × 0.303 = 0.0918 m².
- 12 ÷ 0.0918 = 130.7 tiles; plus 10% = 143.8, so 144 tiles.
- 144 ÷ 10 per box = 14.4, so buy 15 boxes.
A 4 × 3 m floor in 30 × 30 cm tiles with 3 mm joints needs 144 tiles (15 boxes of 10) including 10% waste.
What the result means
Buy all tiles from the same batch (shade and size can vary between batches) and keep a few spares for future repairs.
Assumptions and limits
- A rectangular area. For L-shaped rooms, split into rectangles and add the results.
- The count does not optimise cut pieces; patterned or diagonal layouts typically need 15% or more extra.
- Adhesive and grout quantities are not included.
Questions
How much extra tile should I buy?
Around 10% for a straight lay in a simple room is a common allowance; diagonal and herringbone patterns, or rooms with many corners, need more.
Does the grout joint really matter?
For small tiles, yes. A 3 mm joint on 10 cm tiles adds about 6% to each tile’s footprint, so you need fewer tiles than area ÷ tile size suggests.
Please note: Quantities are estimates. Confirm requirements with your engineer or supplier before ordering materials.