You can count tiles two ways. By piece, you divide the floor by the size of one tile. By box, you divide it by the coverage on the carton. The two should agree, and the box count is the one you actually buy.
Floor area = length × width
Tile area = tile length × tile width
Tiles = floor area × (1 + allowance) ÷ tile area
Boxes = floor area × (1 + allowance) ÷ coverage per box
A 12 × 14 ft floor with 12 × 24 in tiles
A 12 × 24 inch tile covers 2 sq ft of floor. The floor is 168 sq ft, and with a 10% allowance the planner works from 184.8 sq ft. Dividing by the tile’s area gives about 93 tiles.
This example assumes
- 10% allowance for cuts, the planner’s starting value
- Tile face area only; grout lines are not subtracted separately
- A box covering 16 sq ft (eight 12 × 24 in tiles)
Worked example 12 × 14 ft floor, 16 sq ft per box
| Material | Calculated | Buy |
|---|---|---|
| Tile10% waste, 16 sq ft per box | 11.55 boxes | 12 boxes |
The calculation is 11.55 boxes, so the list says 12 boxes. Those boxes supply a little more than the floor needs, and the surplus is your spare tile for repairs.
Two checks that catch mistakes
If the tile you are looking at lists its size, multiply it out and compare it with the coverage on the box. They should agree to within the grout joint. If they do not, one of them is for a different pack size, and the box number is the one the store will sell you.
Large-format tile has its own wrinkle: fewer, bigger pieces mean a cut wastes more of each tile. That is a reason to look at the allowance rather than the area. The waste guide covers it.
What changes the estimate?
- The coverage on the box, which depends on tile size and pieces per box
- The allowance for your layout and tile size
- Grout joint width, which changes how many tiles fit
- Fixed items such as a tub or cabinet the tile stops at
Thinset and grout
Both are optional in the planner. Their coverage depends on the product, the tile and the trowel, so the planner counts bags only when you enter the coverage from the label. Otherwise it lists them as reminders.