How much thinset do I need per square foot?

It depends on trowel-notch size, not just area — a bigger notch lays down a thicker bed and uses more mortar per square foot. As a rough guide, a 1/2in square-notch trowel (typical for 12in tile) uses roughly 3.5-4 lb of dry mortar per square foot; this calculator gives you an exact figure for your tile size and area.

Do I need a different trowel notch for large-format tile?

Yes — larger and heavier tile needs a bigger notch (and often a thicker bed) to get full mortar coverage under a rigid, less-forgiving tile body. Check your tile manufacturer's spec sheet; this calculator's presets follow standard trade convention by tile size.

Do I need a different adhesive for outdoor or wet-area tiling in Australia?

Yes — for wet areas, balconies and outdoor tiling, use a flexible, water-resistant adhesive compliant with AS ISO 13007, and make sure waterproofing (per AS 3740) is applied to the substrate before tiling.

Tile Adhesive Calculator — How Much Do I Need?

Thinset Mortar Calculator: How Many Bags Do I Need?

Thinset mortar is bought by the bag, but how much you need depends on a number most people never measure directly: the thickness of the bed under the tile, which is set by your trowel's notch size. This calculator takes your tiled area and a tile-size preset (which sets the trowel notch and bed thickness for you), then works out the mortar volume, total weight, and bag count so you're not guessing at the checkout.

How to use the thinset calculator

Enter the length and width of the area you are tiling.
Pick a tile-size preset (mosaic through 12in+) — each one sets the standard trowel notch and resulting mortar-bed thickness for that tile size.
Adjust the waste percentage if needed (5-15% covers ridge collapse under the tile and trowel-mark inconsistency).
Enter your bag weight and price per bag to get a bag count and materials cost.

The thinset calculation, explained

Mortar volume = area x bed thickness. Weight = volume x mortar density x (1 + waste%). Bags needed = weight / bag weight, rounded up to the next whole bag.

Worked example: a 4m x 3m floor (12 m²) using 12in x 12in tile (5.0mm bed thickness from the preset table), with a 10% waste allowance and a 25kg bag.

Volume = 12 m² x 0.005m = 0.06 m³.
Weight = 0.06 m³ x 2,162 kg/m³ x 1.10 = 142.7 kg.
Bags = 142.7 / 25 = 5.7, rounded up to 6 bags.

Pro tips

At a typical Australian price of around $22 per 25kg bag of tile adhesive, the worked example above (a 12 m² floor, 300 x 300mm tile, 10% waste, 6 bags) costs roughly $132 in material — tile and a tiler's labour are the bigger cost drivers on most floors.

Trowel notch size should match tile size, not personal preference — a notch too small starves large-format tile of enough mortar contact, and one too large wastes mortar and risks squeeze-out into the joints.
Back-butter large-format tile (12in/300mm and up) — spread a skim coat on the tile back as well as combing the floor — to close voids and get full mortar coverage under a rigid, less-forgiving tile.