Thinset consumption depends mostly on the trowel: the bigger the notch, the thicker the mortar bed. Pick the tile size and the calculator suggests the trowel and whether to back-butter, then counts the bags.
Coverage comes from data sheets (Laticrete, Custom Building Products, Mapei and Brazilian makers). You can type the exact number from your bag.
How to use
- Enter the area to tile.
- Pick the tile size. The calculator suggests the notch: 1/4 × 1/4 in for small tiles, 1/2 × 1/2 in for large formats.
- Tick back-buttering for tiles larger than about 12 × 12 in, outdoors and in showers.
- Choose the bag size to get the number of bags.
Thinset by trowel notch
| Trowel | Single coat (lb/100 sq ft) | Back-buttered (lb/100 sq ft) | One 50 lb bag covers |
|---|---|---|---|
| 1/4" × 1/4" | 59.4 | 90.1 | 84.2 sq ft |
| 5/16" × 5/16" | 67.6 | 98.3 | 74 sq ft |
| 1/4" × 3/8" | 77.8 | 108.6 | 64.2 sq ft |
| 1/2" × 1/2" | 131.1 | 161.8 | 38.1 sq ft |
Without waste. Rough or uneven floors use more.
Which trowel for which tile
Small tiles (under about 8 × 8 in): 1/4 × 1/4 in square notch. Up to 12 × 12 in: 1/4 × 3/8 in. Larger tiles and plank-style tiles: 1/2 × 1/2 in, back-buttering the tile. Industry standards ask for at least 80% mortar contact on dry indoor floors and 95% in wet areas and outdoors.
Double coating
Back-buttering means spreading a thin layer on the back of the tile as well as on the floor. It uses more thinset but avoids hollow spots under large tiles, which crack under load.
Where the numbers come from
Coverage and consumption figures come from manufacturer data sheets and published standards: