Building
Tile Calculator
Tiles, boxes, adhesive and grout for floors and walls, by pattern.
How this calculator works
The calculator divides your area by the area of one tile, then adds waste: 10 percent for a straight lay, 15 percent for diagonal because every edge row needs angled cuts. If you tell it how many tiles come in a box it rounds up to whole boxes.
Adhesive is estimated at 3.5 kilograms per square metre, which suits a 6mm notched trowel on floors. Large format tiles and back buttering push usage higher.
Grout depends on tile size and joint width: the calculator works out the joint volume around your tiles and multiplies by 1.8 kilograms per litre, the typical density of mixed grout.
| Tile size | Tiles per m² | With 10% waste |
|---|---|---|
| 300 × 300mm | 11.1 | 13 |
| 450 × 450mm | 4.9 | 6 |
| 600 × 300mm | 5.6 | 7 |
| 600 × 600mm | 2.8 | 4 |
| 900 × 600mm | 1.9 | 3 |
| Tile type | Joint width |
|---|---|
| Rectified porcelain | 1.5mm to 3mm |
| Standard ceramic floor | 3mm to 5mm |
| Walls | 1.5mm to 3mm |
| External and natural stone | 5mm plus |
Check your tile datasheet: rectified tiles allow tighter joints than pressed edges.
Frequently asked questions
How much extra tile should I buy for waste?
Add 10 percent for a straight lay and 15 percent for diagonal patterns or rooms with lots of corners. Keep a few spares after the job for future repairs, because matching a discontinued tile is nearly impossible.
How much tile adhesive do I need per square metre?
About 3.5 kilograms per square metre with a 6mm notched trowel. A standard 20kg bag covers roughly 5 to 6 square metres on floors, less for large format tiles that need back buttering.
How much grout do I need?
It scales with joint width and tile size: small mosaics with wide joints use many times more grout than large format tiles with 1.5mm joints. This calculator works the volume out from your exact tile and joint sizes.
What is the difference between straight and diagonal laying?
Diagonal laying rotates tiles 45 degrees to the walls. It looks great and hides out-of-square rooms, but every wall row needs diagonal cuts, so allow 15 percent waste instead of 10.
Should I buy all my tiles at once?
Yes, and from the same batch number. Tile batches vary slightly in shade and size calibration, and a top-up box from a different batch can be visibly different once laid.
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