Advanced options
Adhesive coverage assumes solid-bed fixing (about 3.5 kg/m2 with a 6mm notch trowel, 5-6 kg/m2 at 10mm); powdered adhesive for floors and large tiles, and always for porcelain. Grout is calculated from tile size, thickness and joint width, plus 10% waste.
What The Tile Adhesive And Grout Calculator Works Out
- Adhesive: the area multiplied by a coverage rate set by the trowel, not the tile: about 3.5 kg/m2 with the 6mm notch used on walls and 5 kg/m2 with the 10mm notch used on floors and large formats. A 10 m2 floor wants around 50 kg, so three 20 kg bags with a margin.
- Grout: pure geometry. Joint volume per square metre is the tile perimeter over its area, multiplied by tile thickness and joint width, then by grout density of about 1.8 kg per litre, plus 10% waste. Small tiles are grout-hungry: metro tiles at a 3mm joint use several times the grout of 600mm squares on the same wall.
- Solid-bed fixing: the figures assume adhesive combed over the whole surface and tiles pressed to full contact. Dot-and-dab tiling leaves hollow voids that crack floor tiles and fail in showers. Porcelain and anything over 300mm square needs powdered adhesive; ready-mixed tubs suit only small ceramic wall tiles in dry rooms.
- Adhesive coverage override (advanced): replace the built-in 3.5 or 5 kg/m2 with the figure from your adhesive's bag, for example 6 kg/m2 for a 12mm notch on uneven floors or 2.5 kg/m2 for thin-bed wall fixing.
- Grout and tile wastage (advanced): the 10% grout allowance and a separate 10% tile cutting allowance, both editable. Diagonal layouts, herringbone and rooms with many obstacles justify 15% on tiles; a plain square room with large tiles can get away with 5%.
- Bag sizes (advanced): adhesive comes in 20, 10 and 5 kg bags and grout in 2.5 to 10 kg; pick what your supplier stocks and the calculator rounds up to whole bags.
- Tiles to buy (advanced): the area divided by the footprint of one tile plus one grout joint on each side, rounded up after wastage. Check the box count: tiles are sold by the box, usually 1 to 1.5 m2 each.
- Costs (advanced): whole bags multiplied by their price, plus tile area (with wastage) at your price per m2. Typical UK prices are GBP 15 to GBP 25 for a 20 kg bag of flexible adhesive and GBP 7 to GBP 12 for 2.5 kg of grout; porcelain tiles run from about GBP 20 to GBP 60 per m2. The breakdown table lists every line.