Wall & Floor Tile Calculator (Tiles, Boxes, Grout & Adhesive)
Estimate the number of tiles, boxes, tile adhesive, and grout for tiling a floor or wall from the surface size, tile size, grout joint, and adhesive coverage. Metric and imperial.
Surface 12.00 m²; 131 tiles before the 10% waste allowance. Adhesive assumes 20 kg bags. Buy about 145 spacers (one bag) and keep spare tiles from the same batch.
How this works
Tile count is the surface area divided by the area one tile covers, including its grout joint:
surface = L × W
tile area = (tileW + joint) × (tileL + joint)
tiles = ceil(surface / tile area) × (1 + waste%)
boxes = ceil(tiles / tiles per box)
grout = jointW × jointD × (tileL+tileW)/(tileL×tileW) × ρ × areaGrout uses a density of about 1.7 kg/L; adhesive is the area times the coverage rate (about 3.5 kg/m² for walls, 5 for floors, 7 for large format).
Worked example
A 4 m × 3 m floor (12 m²) with 300 × 300 mm tiles, a 3 mm joint, 10 tiles per box, 5 kg/m² adhesive, 10% waste:
- tile area =
0.303 × 0.303≈ 0.0918 m²; tiles =ceil(12 / 0.0918)= 131 - with waste =
ceil(131 × 1.10)= 145 tiles → 15 boxes - adhesive ≈
12 × 5 × 1.10= 66 kg → 4 bags; grout ≈ 3.6 kg
Sources
- Standard tile-grout coverage formula; adhesive coverage rates from tile-adhesive manufacturer guides. Confirm against your product's coverage chart.
FAQ
How do I calculate how many tiles I need?
Divide the surface area you are tiling by the area one tile covers, including its grout joint, then round up and add a waste allowance for cuts and breakages. For a 4 m × 3 m floor (12 m²) using 300 × 300 mm tiles with a 3 mm joint, each tile covers about 0.092 m², so you need roughly 131 tiles before waste. This calculator does the arithmetic and also works out boxes, adhesive, and grout.
How much waste should I add for tiling?
Ten percent is a sensible default for a straightforward layout with straight edges. Increase it to 12 to 15 percent for a diagonal or herringbone pattern, for large-format tiles where a single break wastes a lot, and for rooms with many cuts around fixtures, pipes, and alcoves. Buy a little extra from the same batch as well, because tile colours vary slightly between production runs and a later top-up may not match.
How much tile adhesive do I need?
Adhesive use depends on the trowel notch and the tile size. As a guide, budget about 3.5 kg per m² for small wall tiles, around 5 kg per m² for standard floor tiles, and 6 to 8 kg per m² for large-format tiles that need a deeper bed and back-buttering. This calculator multiplies your area by the rate you choose and divides by a 20 kg bag. Uneven substrates that need extra bed thickness use more, so round up.
How is the grout quantity calculated?
Grout fills the joints, so the quantity depends on the tile size, the joint width, and the joint depth (which is roughly the tile thickness). Smaller tiles have more joints per square metre and use more grout; wider or deeper joints use more again. The calculator uses the standard grout coverage formula and a typical grout density of about 1.7 kg per litre. Treat it as a planning figure and check the bag's own coverage chart.
What grout joint width should I use?
Joint width is partly aesthetic and partly practical. Rectified tiles with very straight edges can be laid with narrow 2 to 3 mm joints for a seamless look; pressed tiles with slightly irregular edges usually need 3 to 5 mm to absorb the variation. Floor tiles and outdoor or wet areas often use wider joints for grip and movement. Larger joints also mean fewer tiles and more grout, both of which the calculator accounts for.
Does this include trim, thresholds, and underlayment?
No. The calculator estimates the field tiles, the boxes, the adhesive, and the grout. Edge trim, bullnose or border tiles, thresholds, movement joints, waterproofing (tanking) in wet areas, decoupling or backer boards, and levelling compound for an uneven substrate are all separate items. Measure trim by the linear metre of exposed edge and size waterproofing and backer board by the same surface area.