Tiles per square metre
Each tile takes up its own size plus one grout joint on two sides. Divide a square metre by that footprint and you have the count. For a 600 × 600 tile with 3 mm joints the footprint is 603 × 603 mm, so 2.75 tiles per square metre. The calculator adds your waste allowance to the area first and then rounds up to whole tiles, and to whole boxes if you enter the box coverage from the carton.
tiles per m² = 1 ÷ ((length + joint) × (width + joint)), in metres
| Tile | Per m², 3 mm joints | 10 m² with 10% waste |
|---|---|---|
| 1200 × 600 | 1.4 | 16 |
| 900 × 600 | 1.8 | 21 |
| 600 × 600 | 2.8 | 31 |
| 600 × 300 | 5.5 | 61 |
| 450 × 450 | 4.9 | 54 |
| 300 × 300 | 10.9 | 120 |
| 200 × 200 | 24.3 | 268 |
| 300 × 75 subway | 42.3 | 466 |
Waste
Every wall you tile up to and every corner you tile around produces a cut tile, and the offcut is usually too small to use anywhere else. In a square room with a straight layout that comes to about 10 percent. Diagonal layouts, herringbone, and rooms with lots of nibs, niches and returns push it to 15 percent, and mosaics or a very large tile in a small room can go higher because a single broken tile is a big fraction of the job. Keep a few spares from the same batch, since the next batch will not match.
Adhesive
Cement-based adhesive is spread with a notched trowel, and the notch sets the bed thickness and therefore the coverage. Floors use a 10 or 12 mm notch, and a 20 kg bag does about 4 to 5 square metres. Walls use a 6 mm notch and a bag does about 7. Large format tiles, 600 × 600 and up, need a full bed with no voids, so they are back-buttered as well, and the coverage drops. Follow the bag for the exact figure and for the right adhesive for the substrate: a flexible adhesive over timber or sheet flooring, a rapid-set where the floor has to be walked on the same day.
Grout
Grout quantity is the volume of the joints. The calculator works out the total joint length per square metre from the tile size, multiplies by the joint width and the tile thickness, and converts to kilograms at about 1.6 kg per litre. Big tiles with narrow joints need very little, small tiles and mosaics need a lot. Grout comes in 1.5, 5 and 20 kg bags, and the calculator shows 5 kg bags.
Worked example
A bathroom floor 3 × 2.4 m in 600 × 600 porcelain, 10 mm thick, 3 mm joints, straight layout. Area 7.2 m², with 10 percent waste 7.92 m². At 2.75 tiles per square metre that is 22 tiles, or six boxes of four. Adhesive at 4 m² a bag for large format is two 20 kg bags. Grout is about 1.4 kg, so one 5 kg bag with plenty left for the skirting tiles.
Common questions
How many tiles per m²?
600 × 600 are 2.8 per m² with 3 mm joints, 450 × 450 are 4.9, 300 × 300 are 10.9. Add 10 percent.
How much adhesive per m²?
A 20 kg bag does 4 to 5 m² of floor or about 7 m² of wall.
How much grout?
About 0.2 kg/m² for 600 × 600 tiles, 0.3 kg/m² for 300 × 300, much more for mosaics.
How much waste on tiles?
10 percent straight, 15 percent diagonal or patterned, and keep spares.
Quantities only. Adhesive type, waterproofing and falls in wet areas follow AS 3958 and AS 3740 and the product data sheets.