The most common mistake when buying tile adhesive is guessing the quantity. The result is either a half-used bag left in the garage, or a second trip to the store mid-installation. Consumption depends mainly on two things: the tile's size and the notch of the trowel you spread it with.
Why tile size matters
The larger the tile format, the thicker the adhesive bed needs to be to sit flat with no air pockets underneath. A small mosaic piece wants a thin layer; a 60×60 cm or larger slab needs a coarser notch and a thicker bed, often with adhesive buttered onto both surfaces.
The consumption formula
Manufacturers state consumption in kg per square metre for a given notch size. A typical rough breakdown:
- 6 mm notch — about 3–4 kg/m² — small format up to 20×20 cm.
- 8 mm notch — about 4–5 kg/m² — medium format up to 33×33 cm.
- 10 mm notch — about 5–6 kg/m² — large format up to 60×60 cm.
- 12 mm notch with buttering — over 7 kg/m² — large format and rectified tiles.
To get to a number of bags, multiply the per-square-metre consumption by the room's area and divide by the bag weight. Always round up with a 10% reserve — an uneven base, cut tiles at the edges and ordinary mixing waste all call for it.
An example
An 8 m² bathroom with 33×33 cm tile and an 8 mm notch: 8 m² × 4.5 kg/m² = 36 kg, plus a 10% reserve, is about 40 kg — two 25 kg bags, with a little left over for a future repair.
If you are not sure which notch to use, bring the tile's packaging to the store — we will work out the quantity together before you pay.
