Formula
Tile area is length times width, in metres. Tiles to buy are the room area divided by that, multiplied by one plus waste, then rounded up.
Boxes are the tiles divided by the number in a box, rounded up.
Adhesive uses the measured area, not the waste allowance. Grout kilograms per square metre are joint width times joint depth times the sum of the tile sides times density, divided by the tile area. That is a geometric estimate.
Worked example
One tile is 0.36 m². 10 m² with 10% waste is 30.6 tiles, rounded up to 31, 8 boxes at 4 tiles.
Adhesive uses the measured area, not the waste: 40.0 kg, 2 bags. Grout is about 0.96 kg. Check the bag coverage table.
Assumptions
The example tile is 600 × 600 mm, 4 to a box, with 10% waste. 15% is there for diagonal cuts.
Adhesive starts at 4 kg per square metre and a 20 kg bag. Grout starts at a 3 mm joint, 6 mm deep, and 1600 kg per cubic metre.
Use the coverage table on the grout bag if you have it. This estimate does not know the tile edge or the joint profile.
Checked
Checked 10 November 2026. Bunnings lists Dunlop tile adhesive in 20 kg bags. Tiles per box, the 4 kg/m² adhesive rate and the grout density were not on that listing, so those stay figures you read off the pack.