Tile calculator - tiles, boxes, adhesive and grout

Boxes = area × (1 + waste) / m² per box, rounded up. The number of tiles is the area with waste divided by the tile area including the joint.

Example: a 4 × 3 m floor is 12 m². With 60 × 60 cm tiles, 2 mm joints and straight lay (5%): 12 × 1.05 = 12.6 m². Tiles: 12.6 / (0.602 × 0.602) = 34.8 → 35 tiles. Boxes of 1.44 m²: 12.6 / 1.44 = 8.75 → 9 boxes (12.96 m²).

Buy all tiles from the same batch (same shade and calibre code on the box). A box bought weeks later may not match. A spare box is also handy for future repairs.

Adhesive depends on the trowel notch, so on tile size: up to 30 × 30 cm about 3-4 kg/m², 60 × 60 cm about 5-6 kg/m², large formats with back-buttering 7-8 kg/m². For 12 m² at 5 kg/m² you need 60 kg - three 25 kg bags.

Grout: kg/m² = (A + B) / (A × B) × tile thickness × joint width × 1.6 (all in mm). For 600 × 600 mm tiles, 9 mm thick, with 2 mm joints: 1200 / 360,000 × 9 × 2 × 1.6 = 0.096 kg/m², about 1.2 kg for 12 m². Small mosaics with 3 mm joints need around 0.6 kg/m².

Dry-lay a few tiles or mark reference lines so narrow cuts do not end up in a prominent doorway. Include the joint width when checking the final row against the wall, and confirm that the substrate is flat and suitable for the tile material. Order enough from one production batch to cover the measured area and chosen waste allowance. Keep a labelled spare tile or unopened box for a later repair, since a replacement batch may have a different shade or calibre. Adhesive and grout coverage varies by product, substrate and installer, so use the manufacturer guidance for the final purchase.