The Complete Guide to Estimating Floor and Wall Tiles
Buying too few boxes means running short mid-room and risking a different dye-lot batch that doesn't quite match. This calculator covers not just the tiles themselves, but the grout and adhesive needed to actually install them — both commonly missed in simpler tile calculators.
Why Box Coverage Isn't One Fixed Number
Even major Australian tile retailers don't hardcode a single "m² per box" figure across every tile size — it genuinely varies by manufacturer, tile thickness, and packaging. Check the actual coverage stated on your chosen product (usually printed on the box or listed on the supplier's website) and enter it above for an accurate box count.
Grout and Adhesive
Grout usage follows a standard formula based on tile size, joint width, and tile thickness — smaller tiles need more grout overall because there's more total joint length per square metre. Adhesive coverage depends heavily on tile size: standard tiles typically use around 4.5m² per 20kg bag with a 10mm notched trowel, but large format tiles (600mm and above) drop to roughly 3m² per 20kg bag, since they need a larger trowel notch and often require "back-buttering" (adhesive applied to both the substrate and the tile back) for full, void-free coverage.
Frequently Asked Questions
Enter your tile size, joint width and tile thickness above and the calculator works out the grout weight for you. As a rough guide, smaller tiles and wider joints both increase how much grout a job needs, since there's more total joint length to fill per square metre.
The calculator estimates adhesive bags based on your total area and tile size. Standard tiles typically use around 4.5m² per 20kg bag, while large format tiles (600mm and above) use closer to 3m² per bag, since they need a bigger trowel notch and often require back-buttering.
Large tiles (600mm and above) need a bigger notched trowel to support their weight and prevent hollow spots, and often require back-buttering — adhesive applied to both the floor/wall and the back of the tile. Both factors increase adhesive consumption per square metre compared to standard-sized tiles.
Smaller tiles mean more individual pieces per square metre, which means more total joint length to fill. A room tiled in small mosaics will always need noticeably more grout than the same area in large format tiles, even at the same joint width.
2–3mm is standard for most modern floor and wall tiles, especially rectified (precision-cut) tiles. Wider joints (5–10mm) suit rustic, handmade, or outdoor tiles where slight size variation between pieces needs more room to sit evenly.
Yes, always — you can't buy a partial box. This calculator already rounds the box count up for you, and it's worth buying at least one extra box beyond that for future repairs, since matching the exact dye-lot later can be difficult or impossible.