A tile job is always an area, but the area comes from different measurements depending on the surface. The calculation after that is the same.
Floors: length × width
Measure wall to wall. If the floor is not a plain rectangle, break it into rectangles, measure each one, and add them. A 12 × 14 ft floor is 168 sq ft.
Walls: run × height
For a tiled wall, measure the length of the wall and the height you will tile to. A wall tiled to 8 ft over a 10 ft run is 80 sq ft. If the tile stops partway, measure to where it stops, not to the ceiling. The planner’s “I already know the area” option takes that number directly, so you do not have to turn a wall into a floor.
Backsplashes: measure the strip, subtract the gaps
A backsplash is usually a long, short rectangle. Say it runs 10 ft along the counter and is 18 inches tall, which is 1.5 ft: that is 15 sq ft. A 2 × 3 ft window in the run takes out 6 sq ft, leaving 9 sq ft of tile.
Backsplash = run length × tiled height
Subtract windows and large openings
Tile area = remaining area, then add an allowance
Worked example 10 ft run, 18 in high, one 2 × 3 ft window, 10 sq ft per box
| Material | Calculated | Buy |
|---|---|---|
| Tile10% waste, 10 sq ft per box | 0.99 boxes | 1 box |
The calculation is 0.99 boxes and the list says 1 box. Small areas make the rounding obvious: a fraction of a box still costs a whole box.
What to subtract and what not to
Subtract windows, doors and large cut-outs that the tile stops at. Outlets and switches are small, and the allowance for cuts covers them. If a niche or inset is large, treat it as an opening.
What changes the estimate?
- Whether the tile runs to the ceiling or stops at a set height
- Large openings you will tile around
- The tile size and box coverage you choose
- The allowance, which matters more on small areas with many cuts
Once you have the areas, the tile count guide turns each into pieces and boxes.