Tile formula
Tiles = floor area ÷ area of one tile, plus waste. Tile area in sq ft = tile length (in) × width (in) ÷ 144. A 12 × 12 in tile is exactly 1 sq ft.
How much waste to add
- Straight lay, simple room: 10%
- Diagonal or herringbone: 15–20%
- Large-format tiles or many obstacles: 15%+
Keep a few spare tiles from the same dye lot for future repairs—later batches often differ slightly in shade.
Grout joints
This estimate ignores grout width, which slightly reduces the tile count—another reason the waste allowance is conservative.