Tile is sold by the box with the coverage printed on the label, so the number to carry to the store is square feet, not a piece count: measure the area, add 10 to 15 percent for cuts, and round up to whole boxes. A 10 x 10 foot floor with 10 percent waste is 110 square feet, which at typical box coverage is about six or seven boxes.
The piece count is only a sanity check. What actually decides your order is the waste factor, and the reason it is not optional is the cut tile at every wall.
Tiles per square foot, by size
You order in square feet, but if you want to check the piece count, divide 144 by the tile's face area in square inches:
| Tile size | Face area | Tiles per sq ft |
|---|---|---|
| 4 x 4 in | 16 sq in | 9.0 |
| 6 x 6 in | 36 sq in | 4.0 |
| 12 x 12 in | 144 sq in | 1.0 |
| 12 x 24 in | 288 sq in | 0.5 |
| 18 x 18 in | 324 sq in | 0.44 |
The tile calculator returns the square feet to buy, the piece count, and the bags of thinset from your room size and tile choice, so you can walk into the store with all three.
Tile by room size
Each row is 12 x 12 inch tile with 10 percent waste and thinset at one 50 pound bag per 75 square feet:
| Room size | Area | To buy | Tiles | Thinset |
|---|---|---|---|---|
| 5 x 8 ft (bathroom) | 40 sq ft | 44 sq ft | 44 | 1 bag |
| 8 x 10 ft | 80 sq ft | 88 sq ft | 88 | 2 bags |
| 10 x 10 ft | 100 sq ft | 110 sq ft | 110 | 2 bags |
| 12 x 10 ft (kitchen) | 120 sq ft | 132 sq ft | 132 | 2 bags |
Always round the square footage up to whole boxes using the coverage on the box, since you cannot buy a partial box.
Waste depends on the layout
Ten percent is the floor, not a universal figure. Match it to how you are laying the tile:
- Straight lay, simple room: 10 percent. Cuts only along the walls, and some offcuts are large enough to start the opposite run.
- Diagonal or herringbone: 15 percent. Every perimeter cut is an angle, and the triangular offcuts are almost all scrap.
- Large-format tile in a small room: 15 percent. A big tile cut to fit a small bathroom wastes most of the trimmed piece.
- Lots of jogs, niches, and pipes: 15 percent or more. Each obstacle is its own set of cuts.
Then, separately, keep a few spare tiles after the job. Dye lots shift between production runs, so a tile that matches your floor is often impossible to source a year later. A handful of spares in the garage is worth far more than the few dollars they cost when you crack one.
Thinset depends on the notch, not just the area
The mortar estimate hinges on trowel notch size, which scales with tile size:
- Small and mid-size tile, 1/4 inch square notch: a 50 pound bag sets roughly 75 to 85 square feet.
- Large-format tile, 1/2 inch notch plus back-buttering: the same bag covers only 40 to 50 square feet, because the ridges are deeper and you are spreading mortar on the tile as well as the floor.
So a large-format floor can need nearly double the thinset of a small-tile floor of the same area. Large tile is also slightly bowed from firing, so keep the offset under one third and consider leveling clips to avoid visible lips between pieces.
The subfloor matters more than the tile
The most expensive tile in the world cracks at the grout lines if it is set over a floor that flexes. Tile needs a stiff, flat base: cement board or an uncoupling membrane over a wood subfloor, with deflection held within L/360.
Get the base right before you spend on tile. The plywood subfloor guide sizes the sheathing underneath, and the flooring calculator compares the material options if tile is one of several you are weighing.