How to calculate grout for any tiled surface
The grout formula uses the tile dimensions, joint width, tile thickness and total area. Larger tiles need less grout (fewer joints per m²); smaller tiles like subway tiles need significantly more. This calculator uses the industry-standard formula used by Australian tile suppliers.
Grout joint width — what's right for my tiles?
- 2–3 mm — rectified tiles (precision-cut, consistent size). Gives a clean, modern look.
- 3–5 mm — standard floor and wall tiles. Most common for bathrooms and kitchens.
- 5–10 mm — natural stone, handmade or non-rectified tiles where size varies.
- 10+ mm — rustic, large-format outdoor pavers or deliberate design choice.
Check your tile manufacturer's recommendation — some tiles specify a minimum joint width to accommodate size variation.
Unsanded vs sanded grout
Unsanded grout is used for joints up to 3 mm — it's smoother and won't scratch polished or delicate tile surfaces. Sanded grout is used for joints 3 mm and wider — the sand gives it strength and prevents cracking in wider joints. For exactly 3 mm, either works; most tilers use unsanded for wall tiles and sanded for floor tiles at that width.
Epoxy grout
Epoxy grout is increasingly popular in Australian kitchens and bathrooms — it's stain-resistant, doesn't need sealing and lasts much longer than cement grout. It's more expensive and harder to work with, but for benchtops, wet areas and high-traffic floors it's worth the investment. Coverage rates are similar to standard grout, so this calculator applies to epoxy grout too.
Standard bag sizes in Australia
Grout is sold in 2 kg, 5 kg and 10 kg bags at Bunnings, Beaumont Tiles and tile suppliers. The 2 kg bag suits small areas like a splashback; the 5 kg covers most bathroom floors; the 10 kg is for larger projects. Always buy slightly more than calculated — colour-matching a different batch later is difficult.