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.
Grout calculator — frequently asked questions
How much grout do I need per square metre?
It depends on tile size and joint width. Smaller tiles with wider joints need significantly more grout than large tiles with narrow joints. For 600 × 600 mm tiles at a 3 mm joint, you need roughly 0.3–0.4 kg of grout per m². For 100 × 100 mm mosaic tiles at 3 mm joints, it rises to 1.5–2 kg per m². The calculator works this out based on your exact tile size and joint width.
What is the difference between sanded and unsanded grout?
Sanded grout contains fine sand aggregate and is used for joints wider than 3 mm — it resists shrinkage and cracking in wider joints. Unsanded grout is smoother and used for joints under 3 mm, particularly on wall tiles and polished surfaces where sanded grout could scratch the tile face. Using the wrong type causes cracking or surface damage.
How long does grout take to dry in Australia?
Most cement-based grouts are firm enough to clean within 15–30 minutes in Queensland's warm conditions. Avoid walking on grouted floors for at least 24 hours. Full cure takes 72 hours before heavy use or cleaning with strong products. Epoxy grout takes longer to cure but is far more durable and stain-resistant.
Should I seal grout in a bathroom?
Yes — always seal cement-based grout in wet areas. Unsealed grout absorbs water, soap scum and mould, which causes discolouration and deterioration over time. Apply a penetrating grout sealer 72 hours after grouting and reseal every 1–2 years depending on the level of use and cleaning products used.
What colour grout should I use with white tiles in Australia?
White or off-white grout with white tiles creates a seamless, contemporary look popular in Australian bathrooms and kitchens. Light grey grout shows less discolouration over time and is increasingly popular. Dark grout creates contrast and hides staining well but can visually shrink a small room. Ultimately it's a personal preference — there's no wrong answer.