Work out tiles, adhesive and grout
Area, tile size and joint. Adhesive by trowel notch, grout by the joint volume.
Adhesive and grout are worked out on the net area plus 10%. Grout = (L + W) ÷ (L × W) × joint width × depth × density.
Quantities are estimates for ordering. Use the adhesive and grout manufacturer's data and buy tiles from one batch.
Tiles per m², grout and adhesive
Common tile sizes and the figures the calculator uses.
| Tile mm | Tiles / m² | Grout 2 mm | Grout 3 mm | Depth |
|---|---|---|---|---|
| 100 × 100 | 100.0 | 0.38 | 0.58 | 6 mm |
| 150 × 75 | 88.9 | 0.45 | 0.67 | 7 mm |
| 200 × 200 | 25.0 | 0.26 | 0.38 | 8 mm |
| 300 × 300 | 11.1 | 0.17 | 0.26 | 8 mm |
| 300 × 600 | 5.6 | 0.14 | 0.22 | 9 mm |
| 600 × 600 | 2.8 | 0.11 | 0.16 | 10 mm |
| 1200 × 600 | 1.4 | 0.08 | 0.12 | 10 mm |
Grout = (L + W) ÷ (L × W) × joint width × joint depth × 1.6, all in mm, giving kg/m². Depth is taken as the tile thickness shown. Tiles per m² ignores the joint.
| Trowel | kg/m² | m² per 20 kg |
|---|---|---|
| Mosaic / 3–4 mm notch | 1.7 | 11.8 |
| 6 mm notch | 2.5 | 8.0 |
| 8 mm notch | 3 | 6.7 |
| 10 mm notch | 3.5 | 5.7 |
| 12 mm notch / solid bed | 4.5 | 4.4 |
Manufacturers' figures range widely (about 1.8–2.8 kg/m² for 6–10 mm notches on a lightweight flexible adhesive, up to 4–5 kg/m² for standard adhesives) — check your bag.
How to work out tiles
Area = length × width (or wall width × height), less anything not tiled such as a bath or window. Tiles = area ÷ area of one tile, plus waste for cuts and breakages:
- Straight lay: add about 10%.
- Diagonal or herringbone: add about 15% — up to 20% for complex layouts with lots of cuts.
Buy whole boxes from one batch and keep a few spare tiles for future repairs.
Grout formula
Grout (kg/m²) = (tile length + tile width) ÷ (tile length × tile width) × joint width × joint depth × density, with all sizes in mm. Most cement grouts have a density factor of about 1.4–1.75 (1.6 is typical). Example: 300 × 300 mm tiles, 4 mm joints, 10 mm deep → 600 ÷ 90,000 × 4 × 10 × 1.6 = 0.43 kg/m².
Adhesive
The bigger the tile, the bigger the notch: 3–6 mm for mosaics and small wall tiles, 6–10 mm for standard wall and floor tiles, 10–12 mm or a solid bed for large format. Floor tiles and large formats need full coverage with no voids, which uses more. Each adhesive's bag gives its own figure — enter it in the box.
Questions tilers ask
How much extra tile should I order?
About 10% for a straight lay and about 15% for diagonal or herringbone, up to 20% for complex layouts. Round up to whole boxes from the same batch.
How do you calculate grout?
Grout in kg/m² = (tile length + tile width) ÷ (tile length × tile width) × joint width × joint depth × density, with sizes in mm and density around 1.6. For 300 × 300 mm tiles with 4 mm joints 10 mm deep that is about 0.43 kg/m².
How much tile adhesive per m²?
It depends on the trowel and the adhesive. As a guide about 2.5 kg/m² with a 6 mm notch, 3.5 kg/m² with a 10 mm notch and 4–5 kg/m² for a 12 mm notch or solid bed. Use the figure on your adhesive bag.
How many 600 × 300 tiles in a square metre?
5.56 tiles, so 6 whole tiles per m² before waste. For 10 m² straight laid with 10% waste you need 62 tiles.
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See Graftum estimatingQuantities are estimates for ordering. Use the adhesive and grout manufacturer's data and buy tiles from one batch.