How it is calculated
The area to tile is length × width (or height for walls) minus anything that stays untiled. Waste for cuts depends on the pattern: 10 % for straight and offset, 15 % for diagonal and 20 % for herringbone. Adhesive is taken from the trowel notch size, and grout uses the standard manufacturer formula based on tile size, joint width and tile thickness.
Tiles = area × (1 + waste) ÷ (tile length × tile width)Adhesive ≈ area × 3–5.5 kg/m² depending on the notchGrout, kg/m² = (A + B) ÷ (A × B) × joint × thickness × 1.6 (all in mm)Example
A 3 × 2 m floor with 60 × 60 cm tiles laid straight needs 19 tiles, or 5 boxes of 1.44 m². Adhesive with an 8 mm notch: about 25 kg. Grout with 2 mm joints: under 1 kg.
Tips from practice
- Large-format tiles (60 cm and more) need a 10–12 mm notch and adhesive on both the floor and the tile.
- Order an extra box for repairs: the same shade may not be available later.
- Check that every box has the same shade and calibre code.
Questions and answers
How much extra tile should I buy?
10 % for a straight pattern, 15 % for diagonal and about 20 % for herringbone or rooms with many corners.
How much tile adhesive per m²?
Roughly 3 kg with a 6 mm notch, 4 kg with 8 mm, 4.5 kg with 10 mm and 5.5 kg with 12 mm. Check the bag of your adhesive.
Why is so little grout needed?
Big tiles with narrow joints have very few joints per square metre. Small mosaics with wide joints need several times more.
Found a mistake in a formula? Write to [email protected]