How to use this calculator
- Enter or choose units.
- Enter or choose floor length.
- Enter or choose floor width.
- Enter or choose tile length.
- Enter or choose tile width.
- The tiles to buy (with waste) updates as you type. Use Copy result or Share to keep it.
Method
Tiles = ⌈L × W ÷ [(a + j)(b + j)] × (1 + Waste)⌉; Boxes = ⌈Tiles ÷ Tiles per box⌉
- L, W
- floor length and width
- a, b
- tile length and width
- j
- joint width
Worked example
- Floor = 4 × 3 = 12 m²; one tile = 0.3 × 0.3 = 0.09 m².
- 12 ÷ 0.09 = 133.3 → 134 tiles to cover the floor.
- With 10% waste: 133.3 × 1.1 = 146.7 → 147 tiles = 15 boxes of 10.
A 4 × 3 m floor in 300 mm tiles needs 147 tiles (15 boxes) with a 10% allowance.
What the result means
Buy all tiles from one batch (shade and calibre), and keep a few spares for future repairs. Large-format tiles and diagonal layouts waste more at the edges.
Assumptions and limits
- A rectangular floor; split L-shaped rooms into rectangles and add them.
- Does not plan cuts; a layout drawing can reduce waste for expensive tiles.
Questions
How much tile waste should I allow?
Commonly about 10% for a straight lay in a simple room and 15–20% for diagonal, herringbone or rooms with many corners.
Does the grout joint matter?
Slightly: a 3 mm joint on 300 mm tiles saves about 2% of tiles. It matters more for small tiles and mosaics.
Please note: Quantities are estimates. Confirm requirements with your engineer or supplier before ordering materials.