Input method
Wall or floor dimensions
Openings to subtract (doors, windows; leave at 0 if none)
Tile and joint
| Area | Amount |
|---|
Adhesive and grout
| Adhesive needed (20kg bags) | 0 |
| Grout needed | 0 kg |
| Grout bags | 0 |
How this calculator works
Tile count starts from the net area: gross length × height, minus any doors or windows you've listed. Each tile is treated as taking up its own size plus one grout gap in each direction, so a 300×300 mm tile with a 3mm gap really occupies 303×303 mm of wall or floor. Dividing net area by that footprint gives the raw tile count, and wastage on top covers cuts, breakages and pattern matching at edges. Boxes are then just tile count divided by however many tiles come in the box you're buying, always rounded up since part boxes aren't usually sold.
The grout formula
Grout coverage is worked out from an established tile-industry formula rather than a flat guess, because a flat kg-per-m2 figure varies enormously with tile size and joint width: kg per m² = ((L + W) ÷ (L × W)) × joint width × joint depth × 1.6, with tile length and width (L, W) and joint width in millimetres, joint depth taken as the tile thickness, and 1.6 a standard density factor for grout. Larger tiles with narrower joints use noticeably less grout per square metre than small mosaic-style tiles with wide joints, which this formula captures automatically.
Choosing a wastage allowance
10% suits a simple rectangular room laid in a straight grid. Push it to 15% or more for a room with lots of corners and cuts, a herringbone or diagonal pattern, or large-format tiles where an awkward cut can waste most of a tile. Always buy from the same batch or dye lot in one go: colour can vary slightly between production runs.
What this calculator does not check
It doesn't check subfloor flatness or whether a levelling compound is needed first, whether the substrate needs a primer or waterproof tanking (wet rooms and showers), or how many trims, edge beads or movement joints a room needs. It also assumes a simple grid layout for the visual; a genuine herringbone, brick-bond, or large-format layout with minimal cuts needs a proper setting-out drawing, which is a job for the tiler or a CAD layout, not this page.
Related tools
Tiling straight onto a new concrete floor? Check the slab thickness and mix with the concrete calculator first.