Floor Tile Calculator
Works out floor tiles for a room, with the adhesive. Enter the room size and the tile, and it gives tiles, bags of adhesive and the spare you should keep.
Includes the waste allowance — this is the figure to order.
Share sends a link that reopens these numbers. Copy details pastes the full breakdown as a list.
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.
Adhesive is the part people forget to order. Budget about 1.5 kg per square metre for every millimetre of bed depth — a 6 mm bed over 12 m² is roughly 120 kg, which is six bags.
Floors need the substrate right before anything else. Timber floors flex and will crack grout and tiles unless overboarded or decoupled; a 3 mm deflection across a 600 mm tile is enough.
Frequently Asked Questions
How many floor tiles do I need for a room?
Divide the floor area by the tile size including the joint, then add 10% for cuts. A 4 × 3 m room in 600 × 600 mm tiles takes about 37 tiles.
How much tile adhesive per square metre?
Around 1.5 kg per square metre per millimetre of bed. A 6 mm bed is roughly 9 kg/m², so a 20 kg bag covers a little over 2 m².
Can I tile over a wooden floor?
Only if it is rigid enough. Timber flexes and tiles do not, so the floor needs overboarding with tile backer board or a decoupling membrane. Tiling straight onto floorboards cracks the grout within a year.