What is thinset?
Thinset is an adhesive compound used to install materials, like tiles and bricks, onto substrates, like walls and floors. Thinset is a mixture of cement and sand, with some additives and polymers that make the mixture more flexible, workable, and adhesive.
Thinset vs. mortar — and how to mix thinset
How to mix thinset is very similar to how you mix mortar. However, you can now find dry pre-mixed thinset that needs only water to get activated. Thinset comes in two general types:
- Unmodified thinset — the traditional cement-and-sand mix without polymer additives. Like concrete, it cures stronger in the presence of moisture, making it ideal for surfaces with membrane-type waterproofing that don't absorb water.
- Modified thinset — contains latex or other polymers that improve flexibility and adhesion. It needs to dry well to set properly, so it works best over water-absorbing substrates like concrete and plywood.
Always refer to the packaging of the thinset to know what type is best for your project.
How much thinset do I need?
How much thinset you need depends on the total area of your project and the size of the tiles you wish to install. Larger tiles need thicker thinset to support them, while smaller tiles can use a thinner layer. The required trowel notch depth — and therefore coverage — changes with tile size:
| Tile size (Imperial) | Tile size (Metric) | Trowel notch | Coverage per 50 lb bag | Coverage per 20 kg bag |
|---|---|---|---|---|
| Small ≤ 6" | ≤ 15 cm | 3/16" (3 mm) | ~50 sq ft | ~5.0 m² |
| Medium 6"–12" | 15–30 cm | 1/4" (6 mm) | ~36 sq ft | ~3.5 m² |
| Large 12"–18" | 30–45 cm | 3/8" (9 mm) | ~24 sq ft | ~2.3 m² |
| Extra Large > 18" | > 45 cm | 1/2" (12 mm) | ~16 sq ft | ~1.5 m² |
To achieve a consistent thickness throughout an area, use a notched trowel that leaves a uniform set of thinset beads across the substrate. When the tile is pressed into the beads, they flatten and bond the tile evenly.
How to use our thinset calculator
- Choose your unit system — Imperial (feet) or Metric (meters).
- Enter the area dimensions — length and width of the surface to be tiled.
- Select tile size — this determines the required trowel notch and coverage rate per bag.
- Set wastage allowance — 10% is standard; use 15–20% for complex layouts or diagonal cuts.
- Optionally enter price per bag and choose your preferred currency to get a material cost estimate.
- Click Calculate — the calculator returns the number of bags, total weight, and optional cost.
How to calculate the amount of thinset needed
The formula used in this calculator:
- Project area = Length × Width
- Area with wastage = Project area × (1 + Wastage% / 100)
- Bags needed = ⌈ Area with wastage ÷ Coverage per bag ⌉ (rounded up)
- Total weight = Bags × Bag weight (50 lb or 20 kg)
The coverage rate per bag is determined by the tile size category, which sets the required trowel notch depth. All coverage values follow standard industry guidelines for Portland cement-based thinset mortars.
Want to learn more?
For related calculations, explore our Grout Calculator to estimate the amount of grout needed for your tiling project, or the Concrete Calculator for slab and footing volumes. For tile quantities, our Tile Calculator helps you find out how many tiles you need.