How to calculate how many tiles you need
- Measure the area. Length × width for a floor, or width × height for a wall. Split L-shaped rooms into rectangles and add them up.
- Find the area each tile covers, including its grout joint. A 12 × 24 in tile with a ⅛ in joint takes up 12.125 × 24.125 in.
- Divide the area by the tile area.
- Add extra for cuts and breakage, then round up to whole tiles and whole boxes.
Worked example: a 10 × 8 ft bathroom floor with 12 × 24 in tiles
The floor is 80 sq ft. Each tile covers 2 sq ft, so you need 40 tiles to cover it exactly. With 10% extra for a straight layout that rises to 44 tiles. At 8 tiles per box, buy 6 boxes.
How much extra tile to buy
| Situation | Extra |
|---|---|
| Straight or stacked layout in a simple room | 10% |
| Diagonal, herringbone or chevron layout | 15–20% |
| Many corners, a toilet, pipes or a fireplace to cut around | Add another 5% |
| Large-format tile (24 in / 60 cm and up) | Add a few spare tiles, since one cracked tile is a big loss |
Why keep spare tiles
Tile is made in batches, and color can shift slightly from one batch to the next. Buy everything at once, check that every box has the same batch or lot number, and store a few spare tiles. If one cracks in five years, a matching replacement may no longer be on sale.
For plank flooring sold by the box, use the flooring calculator instead.
Grout joint width
The joint is set by the tile, not by taste. Rectified tiles, which are cut to precise edges, can take joints as narrow as 1/16 in (2 mm). Handmade or rustic tiles vary in size and need wider joints, often 3/16–1/4 in (5–6 mm), to keep the lines straight. The tile manufacturer usually lists a minimum.