Estimate how many tiles you need for a floor or wall from the area and your tile size, with a waste factor for cuts and breakage.
tiles = area_ft² ÷ (tile_l × tile_w ÷ 144) × (1 + waste)
Divide the area by the area of one tile (tile length × width in inches, divided by 144 to get square feet), then add waste.
Use 10% for straight-lay, 15–20% for diagonal or patterned layouts — they need more cuts.
An 8 x 10 ft floor is 80 square feet. With 12 x 12 inch tile (exactly 1 square foot each), you need 80 tiles before waste. A straight-lay pattern carries 10% waste for cuts at the walls, so order about 88 tiles.
If you run the tile on a 45-degree diagonal, every edge tile is a cut and waste jumps to 15-20% — order 92-96 tiles. Buy from a single lot number so the shade matches, and keep a few spares after the job for future repairs.
Coverage is exact geometry. TCNA recommends 10% waste for straight-lay tile and more for diagonal or large-format layouts.
100 tiles before waste — each 12×12 tile covers exactly 1 square foot.