How the tile count is calculated
The first step is finding the area of a single tile. Tile sizes are given in inches, so the calculator multiplies the tile width by its height and divides by 144 to express that area in square feet, the same unit as the room.
Dividing the room area by the area of one tile gives the bare number of tiles that would cover the floor with no offcuts. A waste percentage is then added on top to account for the tiles that get cut at edges and corners, and the figure is rounded up to whole tiles.
How much waste to allow
The waste allowance is the difference between a tidy estimate and running out halfway through a job. How much you need depends mainly on the layout and the room shape.
- Straight, grid layouts in a simple rectangular room: around 10 percent.
- Diagonal or herringbone patterns: 15 to 20 percent, because angled cuts waste more.
- Rooms with many alcoves, pipes, or fixtures: lean toward the higher end.
- Large-format tiles: allow extra, since a single broken or mis-cut tile costs more area.
Buy from one batch
Tiles are manufactured in batches called dye lots, and color and size can vary subtly from one lot to the next. Buying all your tiles at once, from the same lot, avoids a visible mismatch that often only shows up under the right light once the floor is laid.
It is also worth keeping a handful of spare tiles after the job. If a tile cracks years later, a matching replacement from the original lot is far better than the closest thing the store still stocks.
What this estimate leaves out
This calculator counts tiles only. It does not size adhesive, grout, spacers, backer board, or trim pieces, and it assumes a single rectangular area. For complex rooms, calculate each section separately and add the totals. Always confirm the tile's coverage and your layout before ordering, and treat the result as a quantity to buy at minimum.
Formula
tileArea(ft²) = (width(in) × height(in)) / 144; tiles = ceil(roomArea / tileArea × (1 + waste/100))Frequently asked questions
- How much waste should I allow?
- Allow about 10% for straightforward layouts and 15–20% for diagonal patterns or rooms with many cuts.