TradesHow this works
Enter the floor area and the tile size. The tool counts the tiles with a 10 percent waste allowance, picks the trowel that matches the tile, and works out the thinset bags for it plus a rough grout weight. The trowel is the part people get wrong: a bigger tile needs a bigger notch, which covers far less per bag.
That is why a large-format job can burn double the thinset of the same area in small tile, even though it uses fewer tiles. Back-butter large tile for full support, confirm coverage on the actual bag, and buy a little extra for a wavy substrate and dye-lot matching.
Common questions
How many tiles do I need?
Divide the floor area by the area one tile covers, then add for waste. A 12 inch tile covers 1 square foot, so a 120 square foot floor is 120 tiles plus about 10 percent for cuts, roughly 132. A busy or diagonal layout needs more, and it is worth an extra box to match the dye lot later.
How much thinset do I need?
It depends on the trowel, which depends on the tile size. A 1/4 by 1/4 inch notch covers about 80 square feet per 50 pound bag, a 1/4 by 3/8 inch about 60, and a 1/2 by 1/2 inch about 35. A bigger tile needs a bigger notch that spreads thicker, so it covers far less per bag.
What trowel do I use for large-format tile?
For tile larger than 12 inches, use at least a 1/2 by 1/2 inch notch and back-butter each tile, meaning spread a thin coat on the back as well. Large tiles need full mortar contact or they crack, and under-notching leaves voids. When in doubt, size the trowel up.
Why does large-format tile use so much thinset?
The bigger notch lays a thicker bed to fill the space under a big, slightly warped tile and give full support. A 120 square foot large-format job can need around four bags, double what the same area in small tile with a fine notch would take. Fewer tiles, but far more mortar.
How much grout will I need?
Grout depends on tile size, joint width, and tile thickness, so treat the number here as a rough start. Smaller tile has more joint per square foot, so it uses more grout. Confirm against the coverage chart on the grout bag for your exact tile and joint.
Sources: Thinset per 50 lb bag: 1/4x1/4 ~80 sq ft, 1/4x3/8 ~60 sq ft, 1/2x1/2 ~35 sq ft (Inch Calculator, Hunker) · Trowel by tile: 1/4x1/4 to ~8 in, 1/4x3/8 to 12 in, 1/2x1/2 over 12 in (back-butter); grout ~4.5 lb/100 sq ft of 12 in tile at 1/8 in joint. Engine version 1.0.0. Risk tier 1.