How to calculate tiles
Divide the area by the size of one tile plus its grout joint, then add extra for cuts and breakage. For a 10 × 8 ft floor (80 sq ft) with 12 × 24 in tiles (2 sq ft each), you need 40 tiles plus 10%, so 44.
How much extra?
- Straight lay in a simple room: 10%
- Diagonal, herringbone or many corners: 15–20%
- Large-format tiles: at least 10%, since each broken tile is a big loss
Keep a few spare tiles after the job. Matching a discontinued tile years later is almost impossible.