Grout Calculator Australia — How Much Grout Do I Need?
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How to calculate grout quantity in Australia
Grout volume per m² depends on tile size, joint width and tile thickness. The formula is: [(tile length + tile width) ÷ (tile length × tile width)] × joint width × tile thickness, giving a volume in mm per mm² of surface. Convert to litres, multiply by grout density (approximately 1.7 kg/L for standard cement-based grout) and add 10% wastage. Smaller tiles with narrow joints need proportionally more grout than large-format tiles. AS 3958 (the Australian tiling standard) recommends a 10% waste allowance on all grout quantities.
Grout calculator — FAQs
What grout joint width should I use for floor tiles in Australia?
Rectified porcelain tiles (precision-cut, perfectly square edges) can be installed with joints as narrow as 1.5–2 mm. Standard ceramic and non-rectified tiles need 3–5 mm joints to accommodate size variation — AS 3958 recommends a minimum 2 mm joint for most tiles. Natural stone, terracotta and handmade tiles typically suit wider joints of 5–10 mm. Narrow joints need less grout but are more demanding to keep clean over time.
What is the difference between sanded and unsanded grout?
Unsanded grout (fine grout) is used for joints up to about 3 mm wide — it is smoother and less likely to scratch polished tile surfaces. Sanded grout is used for joints 3 mm and wider — the sand aggregate reduces shrinkage and cracking in wider joints. Using unsanded grout in wide joints will result in cracking; using sanded grout in narrow joints risks scratching polished porcelain or marble. Most Australian tiling supply stores (Beaumont Tiles, Tile Junket) stock both types and can advise.
How long after tiling can I grout in Australia?
Standard practice is to wait at least 24 hours after laying tiles before grouting, and 48 hours in cooler or humid conditions. This allows the tile adhesive to cure enough to resist the pressure of grouting. If tiles move or feel springy when pressed during grouting, the adhesive hasn't cured — wait longer. In hot, dry conditions (common in Australian summers) adhesive may cure faster, but 24 hours is the minimum recommended by most adhesive manufacturers.
How do I calculate grout for large format tiles?
Large format tiles (600 × 600 mm or larger) use less grout per m² than smaller tiles because they have fewer joints per unit area. For a 600 × 600 mm tile at 3 mm joint width and 10 mm thickness, you need approximately 0.14 kg/m² — versus about 0.55 kg/m² for a 100 × 100 mm mosaic tile with the same joint and thickness. Use the calculator above with your exact tile dimensions for an accurate result.
Can I use the same grout colour for floor and wall tiles in Australia?
Yes, using the same grout colour throughout a wet area (bathroom, kitchen splash-back) gives a cohesive, clean look. Contrasting grout (dark tiles with light grout or vice versa) creates a grid effect — dramatic on feature walls but can look busy on large floor areas. White or light grey grout shows dirt more on floors; dark grey grout hides dirt but can look heavy on pale wall tiles. Choose a grout colour with a sample board under the actual lighting conditions of the room, not just in the store.