How the tile calculator works
Each tile covers its own size plus one grout joint in each direction.
Tiles = area (sq in) ÷ ((tile length + joint) × (tile width + joint)) × (1 + waste)
Example: an 8 × 5 ft bathroom floor with 12 × 12 in tile
The floor is 40 square feet, or 5,760 square inches. With a 1/8 inch joint each tile covers 12.125 × 12.125 = 147 square inches, so you need 39.2 tiles. With 10% extra, buy 44 tiles: 4 boxes of 11, about $100.
Frequently asked questions
How much extra tile should I buy?
10% for straight layouts and 15% for diagonal or patterned layouts. Large-format tile and natural stone may need more because cuts waste more material.
Should I include the grout joint?
Yes for accuracy, though it matters most with small tiles. The calculator adds it automatically.
Last reviewed: 2026-10-31