Tile Calculator
Works out tiles for a floor or wall from the area and the tile size. The grout joint is included, since a 600 mm tile with a 3 mm joint occupies 603 mm.
Includes the waste allowance — this is the figure to order.
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The formula
units per m² = 1,000,000 ÷ ((face length + joint) × (face height + joint)) units = area × units per m² × (1 + waste)
Each unit effectively occupies its own face plus one joint along two edges, because the joint is shared with its neighbour. Working from the real face size and adding the joint is the only reliable way — nominal sizes already include the joint, so adding one again counts it twice.
What to watch out for
Waste is decided by the layout, not the room:
- Straight, square room: 10%. Cuts from one edge start the opposite one.
- Diagonal: 15%. Every perimeter tile is cut at 45°, and the offcuts are triangles.
- Herringbone or large format: 15–20%. Large tiles waste more because a small cut ruins a big tile.
- Natural stone: add 5% on top — some of every pallet is unusable on colour or flaw.
Frequently Asked Questions
How many tiles do I need?
Divide the area by the size of one tile including its joint. A 12 m² floor in 600 × 600 mm tiles with 3 mm joints needs about 33 tiles, or 37 with 10% waste.
How much extra should I buy for cuts?
10% for a straight layout, 15% for diagonal or large format, 20% for herringbone. Add 5% on top for natural stone, where some of every pallet is unusable.
Should I include the grout joint in the calculation?
Yes, though it rarely changes the answer by much. A 600 mm tile with a 3 mm joint occupies 603 mm, which is about 1% fewer tiles per square metre. On small mosaics the effect is far larger.