The formula
Tile area (sq ft) = (tile width + grout) × (tile length + grout) ÷ 144 (inches) Tiles = room area ÷ tile area, plus extra for cuts
Example: an 8 × 10 ft floor is 80 square feet. A 12 × 12 in tile with a 1/8 in joint covers 1.02 square feet, so the floor takes 78.4 tiles; with 10% extra, buy 87.
Quick answers for common floors
| Floor | 12 × 12 in | 12 × 24 in | 24 × 24 in |
|---|---|---|---|
| 5 × 8 ft (40 sq ft) | 44 | 22 | 11 |
| 8 × 10 ft (80 sq ft) | 87 | 44 | 22 |
| 10 × 12 ft (120 sq ft) | 130 | 65 | 33 |
| 12 × 15 ft (180 sq ft) | 194 | 98 | 49 |
How much extra to buy
- 10 percent for a straight layout.
- 15 percent for diagonal or herringbone patterns and for large tiles.
- A little more for small rooms with lots of cuts. Keep a few spares for repairs.
Tiles per square foot
| Tile size | Tiles per sq ft (no grout) |
|---|---|
| 4 × 4 in | 9 |
| 6 × 6 in | 4 |
| 12 × 12 in | 1 |
| 12 × 24 in | 0.5 |
| 24 × 24 in | 0.25 |
Questions
How much extra tile should I buy?
About 10 percent for a straight layout and 15 percent for diagonal patterns. Keep a few spare tiles; the same batch can be hard to find later.
How many 12 × 12 tiles do I need for 100 square feet?
About 98 tiles before extra with a 1/8-inch joint, so buy around 108 with 10 percent extra.
Does grout width change the tile count?
Slightly. Wider joints mean each tile covers a little more area, so you need a few fewer tiles.