Tile Calculator — How Many Tiles Do You Need?
Tiles are sold individually or by the box, and getting the count wrong means either a return trip or leftover tiles taking up garage space. This calculator accounts for grout joints and adds a waste allowance for cuts, giving you an accurate tile count and box total.
How we calculate
Effective tile area = (tile length + grout gap) × (tile width + grout gap) (converted to m²). Tiles needed = ⌈(floor area ÷ effective tile area) × (1 + waste %)⌉. Boxes = ⌈tiles needed ÷ tiles per box⌉.
Worked example
A 4 m × 3 m room (12 m²) with 600 × 300 mm tiles, 3 mm grout gaps, 10% waste, and 6 tiles per box: effective tile area = 0.603 × 0.303 ≈ 0.1827 m². Raw tiles ≈ 65.7, with waste ≈ 73. Boxes = ⌈73 ÷ 6⌉ = 13 boxes.
Common mistakes
- Ignoring the grout gap — it adds up and means you need slightly fewer tiles than a pure area calculation suggests.
- Not adding waste for cuts — border tiles always need cutting, especially around obstacles.
- Ordering the exact count and being left short when a tile cracks during laying.
- Forgetting to match batch numbers when buying extra boxes after the job starts.
Frequently asked questions
How many tiles do I need for a 4 m × 3 m room?+
With 600 × 300 mm tiles, a 3 mm grout gap, and 10% waste, a 12 m² room needs approximately 73 tiles — about 13 boxes at 6 tiles per box. The exact count depends on your tile size and tiles per box, which you can enter in the calculator.
What grout gap should I use?+
Use 2–3 mm for rectified (precision-cut) tiles laid on flat substrates. Use 5–10 mm for handmade, natural stone, or textured tiles. Always check the tile manufacturer's recommendation, as too-small joints can crack under thermal movement.
How much extra tile should I buy for waste?+
Buy 10% extra for straight lay. Increase to 15% for diagonal (45°) lay, which wastes significantly more at the borders. Always keep a few spare tiles from the same batch for future repairs.
Why do I need to match batch numbers when buying extra tiles?+
Tile colour and surface texture can vary between production batches. Even tiles from the same range can look noticeably different if from different firings. Buy all tiles at once and check that all boxes share the same batch number.